Redmine

We had a QA person setup redmine back in '09 with redmine 0.8.4. She's gone now and we're trying to install the redcase plugin on that version. We've got it installed, and can create test cases under the "New Issue" tab, but for whatever reason, when we click on the "Test Cases" tab we just get the following error message. We've tried this in a few different versions of IE, Chrome, and Firefox.

Internal error

An error occurred on the page you were trying to access.
If you continue to experience problems please contact your redMine administrator for assistance.

If anyone can point us in the right direction, it would be appreciated. I've scoured the internet all day with no luck.

Thanks!