My server went down for a few minutes today and when it came back up it started booting every single user right when they sent text to the chat.

Symptoms:

no usernames show up on the log for entering and leaving members or guests.

I can remain logged into the Admin panel but am booted out of chat and back to the login page. So I can still make changes to the chat/site, but can't chat.

Any Idea what file I should replace from my recent backups in order to fix this?

error logs ?

I know this makes me sound dumb, but where do I find them?

i dont know, try

google tell me this:

/var/www/log

which version of gtchat do you have ?
which server version and Distribution ?

try the safe mode please...

I returned to a backed-up version of the chat, it works now. I'm slowly replacing files, one-by-one, to see which one did it. I'll update when I find it.