Have you tried using a OLEDB driver in your strConnString in config.asp instead of the ODBC driver? I don't know the exact string, but if you do a search on this forum, you'll probably find it.
EDIT - what is the connection string you are using? You can leave out the password and username if you like.
That's fine. But it helps troubleshooting if you let us know what string you are using. Please post it. It could be that your host has made some updates to the web server that may be causing the problem.
You need to add come changes to your database. These topics describe several things done by a user who had the same problen. Read them and apply the fixes there:
Basically the fix is to add a clustered index to the T_LAST_POST column in the FORUM_TOPICS table and to the R_DATE column in the FORUM_REPLY table. Installing SQL Server 2000 Service Pack 2 eventually solved the situation for the user with the previous situation, so I'd suggest you do the same. If your not running SQL Server 2000 make sure you have all the service packs installed also.