I had to do that once. It resulted in a few corrupt databases. You may need to try compiling and find where the corruptions exist. Then copy the code to notepad. Delete existing code and then replace it. That was one way I managed to skip rebuilding. I won't say it was the right thing to do, but on a short time window it did the job until I could convince everyone to just switch to 2007.

Other steps you might want to look into:
1. Convince management to let you switch to 2007 all together
2. Go to the VBE. Click tools and then click references and see if there are any missing references. It is possible that one of the .dll files was copied over, or moved in the installation process. By general standards it's best to not have more than one on a machine, but from experience you can't always convince them.