'tinyMCE.activeEditor' is null or not an object in ie8

I get the above error in ie8 when the Edit Content pop up box appears when I attempt to edit a standard content block. When I go to insert a file using the 'Add File' button and click on Choose from the drop down menu to select a file, the file will not insert. I imagine this probably has something to do with the error. Also, intermittently, I get an 'Object expected' error on - also on the Edit Content pop up box. Is this a bug with c5 or is it an issue with ie8? Has anybody got any ideas? I've Googled it to death without getting anywhere. Any help would be appreciated. We have a large client who, for a variety of reasons, cannot use any other browser other than ie8 and we need to fix the problem rather than simply use an alternative browser.

View Replies:
jonhillfrankdesign replied on at Permalink Reply
Also I've just noticed that the main control panel of the MCE editor which contains all the control items has disappeared. Again, this only occurs in ie8.