SharePoint came up with an “unexpected error”

We are using the Microsoft SharePoint web application platform and have recently upgraded to version WSS3.0. We have about 200 SharePoint sites as well as custom web parts and custom lists. After installing version WSS3.0, we restored the 200 SharePoint sites and database information. The custom lists forms, however, are not functioning. I tried to build a new component in the list and blog but SharePoint came up with an “unexpected error” without any other information appearing in the application and SharePoint logs.
As far as I know, feature definitions should be found in the configuration database so I decided to reinstall all the features. I am still facing the same errors though. Can you please help?
