two words - mod security - on you web server -
http://www.modsecurity.org/
This will help with the script kiddies - and XSS and system injection attacks - if your server or site was compromised it was because the security sucked.
Also I would make sure you have cpanel server locked down - go to the cpanel forums to find out how.
Do you have shell access to the server?
You may want to run rkhunter and see whats up.
If you have been comprimised for a month - well best advice to you is - redo the server - i.e. wipe it clean and reinstall the OS lock it down, install mod security and trip wire - rebuild your forum etc and go from there.
A system that has been hacked for a month is screwed no matter what you do.