1) Make sure you're using our latest SVN code. It works around several Gmod errors since our 'release' in January.
2) The final step of our FAQ I linked to has you provide us key information output after following a command. Please see step 5 "and most importantly" part.
Though indeed the gamemode file may help us spot an issue AFTER that requested information, we'd like to make sure there isn't any corruption in our files first.