My hosting provider has a Concrete5 quick installation option and I went for it 5 days ago. When I tried to modify themes and some CSS I realized there weren't files in my server. So, I decided to install the C5 using the traditional way, via FTP.
I also deleted from my Myphpadmin the database the quick installation created, so I could install the CMS installation from scratch.
As result, when attempting to install the CMS I get the following error message: Unable to connect to database. A database error occurred while processing this request. I don't know what to do now, could you please give me a hand. I will appreciate it!!
In your ROOT > config folder there is a file called "site.php". Rename that to something else and try again. It sounds like you haven't removed all the files/folders and/or you're doing something wrong.