Hi Eric, I have now setup a clean database and reinstalled a clean set of PowerCMS2 files (no updates).
The MySQL version being used is 5.0.51a (please see: link removed).
The problem is still there, you just can't add content with nothing appearing in the Content Sidebar or the Activity List. The 'Manage Uses' and 'Settings' are both working perfectly, with all changes made being passed directly into the database.
Not sure what to try next?