All Internet Explorer Users Cannot Login To Site - CACHE has been cleared!

Guys the weirdest thing is going on with my client's site.
I am VERY DISTRAUGHT and I am begging for someone to help me sort this all out!!!

We've had this site up and running with member registration for over a year and a half now without anything close to this happening before.
(Fyi, the site is
Recently I added some new features/pages to the site, but I honestly can't imagine what I did to cause the problems we are having now. (The only thing I can imagine is that I purchased a redirect app that didn't work for us, so I deleted the whole thing - but I'm still baffled as to how that would cause what I explain below!!)
All users can fully see our home page. When they click on "Radio Archives" from the nav menu bar, they are prompted to login or register. Up until yesterday there was never a problem, but now whenever MOST of my users enter their username and password, it gives no errors at all, but still refuses to log them into the site. I have found that 100% of reported cases to me have been by people on all different Windows OS's (7, Vista, and XP all do this using both IE or Firefox). I cannot replicate the problem on a Mac.

Let me note - the users are NOT seeing outdated information though... if I make changes to the site, it appears immediately for them, yet they still can't login.
I of course cleared my site's cache to make certain it wasn't that, and it has not helped at all.
In every instance I know of, clearing the user's browser history/cookies and such has NO affect on their ability to login (which seems strange to me). Every time that I can think of though, turning their computer off and back on again has fixed the problem.

Unfortunately my client's primary demographic is more elderly people who know almost nothing about computers and we are lucky they are willing to try and use our site at all! Hence problems logging in is literally making them go crazy, DRASTICALLY affecting the likelihood that we will loose a lot of customers due to them having such a traumatizing experience not being able to login even though they have their username/e-mail correct.
This is a humungous deal to my client to say the least. Since we have thousands of registered users (many don't even know what the word "reboot" means), it is near impossible to somehow tell them all to turn off their computer and try again. (Although at the moment I do have a very ugly big announcement on the home page of the site explaining to try that if they can't login.)

I even attempted to make the Radio Archives page we want them to go to have completely open permissions and then I just put in a login box and made all the blocks be hidden to guests... but on WINDOWS computers that have previously logged in, it STILL keeps denying them access (but again, without giving any error messages, which makes it worse!)

If you actually read all of this and are willing to help me,
Thank you from the bottom of my heart!!!!!!!!!!

View Replies:
Phallanx replied on at Permalink Reply
I have seen similar before. It was one of two reasons.

1) Site was set to "username" login, however, users were expected to place their email address as the username login. (check your site settings)
2. An addon (forget which now) added new users with an ID rather than their email address. The result was that users that registered before adding the addon could sign in with their usernames and email addresses but after, if the site was set to email login, they couldn't when the addon was removed. Check your users email addresses and if any are digits only, then it's probably that.
jbx replied on at Permalink Reply
Can I ask - have you personally seen this issue?

I have tested your site on Linux and on Windows 7 with a variety of browsers. Works every time.

What I will say though, is that the error message if you enter your details wrong is hidden down near the bottom of the page. It looks like the page has just reloaded.

Could this be the problem?

medicimedicine replied on at Permalink Reply
Yes I have seen it, but it only applies to users who have previously logged in before, I do not believe brand new users are affected by it.
Phallanx replied on at Permalink Reply
Well. I've seen the issues above.
Just been to your site and I can log in. I did notice however that the form autofills with the email address rather than the username if it was remembered by the browser after registration. Maybe they are assuming that the email address is the correct username as it is already filled out (which it isn't) and just supplying the password (which of course fails)
medicimedicine replied on at Permalink Reply
Unfortunately I don't think either of these two things you mentioned applies to my case.

1) I checked my system and settings and the box next to "use e-mail address for login" is unchecked, so it matches with the fact that at login screen we are asking for username (not e-mail).

2) I truly believe the login issue has nothing to do with what is actually being typed in at all - it is not that they are entering e-mail addresses (although that is an interesting point you make for future to make things more streamlined perhaps), but I personally can guarantee that is NOT the issue right now. Currently previously users on Mac computers can log in and Windows cannot (except USUALLY if they shut down the Windows and then turn it back on, it ends up working, but not always). The usernames themselves are not the problems - there aren't any with just "id's" or anything, and this is applying to users who had been able to log into the site multiple times a week for over a year straight with no problems.
I can still log in as the users going through the dashboard.
I have checked and checked my permissions like a thousand times, and I can find nothing that would not allow people to log in! And the way our site is, there is NO option for removing the login feature as they are paid members accessing material that guests who have not paid do not get.

Thank you for the suggestions so far.

Oy vey!
medicimedicine replied on at Permalink Reply
I feel this has to somehow have something to do with cache or cookies or something, as rebooting or downloading an entirely new web browser seems to always help the issue (although simply clearing the user's computer's browsing/cookie history in IE never solves it). Again, our users don't know to try these things on their own and end up leaving the site.
Why is this affecting 100% of IE Windows users (it seems to only affect those with Firefox if they have been using IE as their primary browser - if we download Firefox new, it always works for them to log in).

I am so baffled by this. Like I say, this kind of thing has never happened before, and I think an add-on or something MUST have added a rogue code in somewhere that Macs just ignore. I don't have a clue how to find that out though.

Please help, thank you!!!
medicimedicine replied on at Permalink Reply
WEIRD note... Also when using a computer that cannot log in, if I simply tell the browser to enter private browsing mode and then attempt to log in, not only does it work, but from then on it has fixed it to be able to log in through non private mode too. (Yet clearing browser data doesn't work! What???)
medicimedicine replied on at Permalink Reply
They had the same problem I do, but supposedly this was fixed a long time ago. Did I somehow unfix it? I tried seeing where to add the lines of code they mentioned, but since I am on 5.5 now (and they were on 5.4) I'm not sure it's the same fix anymore.
karlertl replied on at Permalink Reply
I had the same problem: I couldn't login with IE to my 5.5 sites.

I found out that the problem was caused by the following entries in my config/site.php:
define('BASE_URL', '');
define('DIR_REL', '');

These lines are not generated automatically in 5.5. I added these lines manually because only then the redirection from non-www to www worked properly on my server.

However, I saw that this caused my login problems with Internet Explorer. If I remove the two lines, I can log in without any problems.
Maybe you should try this, too.

To make the redirection work again, I now use the .htaccess file.

diorist replied on at Permalink Reply
Just to confirm a reproducible result, I'm experiencing the exact same login issue. Site works fine in Win 7 FF, Chrome, and Safari. But at least in IE9, login just fails without an error. Logging in under Private Browsing does work (although it doesn't carry over to non-private browsing in my case).

Not a solution, I know...just validation that it's not only you, mm. Will post back here if I find a fix.
medicimedicine replied on at Permalink Reply
Thank you for posting - it is truly exactly my problem. I also found that they could sign in using private browsing. (but that's so unpractical!)
In fact, for some of my people simply downloading firefox and signing in on that suddenly made IE work again (I think if the settings are to share info between browsers). It HAS to be that IE is rejecting the cookies that everyone else in the world accepts.... my mom says that's called being a brat and not playing nice with others! :-)
datatainment replied on at Permalink Reply
Same here, but it doesn't seem to be related to IE and C5 only.
with IE8 i can't login on the productive version of the website, but to the developer version on the local network server (without intranet settings).
clearing the cache or using private-mode doesn't do the trick.
so i guess it's a server-setting AND c5 issue.

anyone else experienced this?