I already mentioned the vb version.. its the latest..
And the hacks:
File Uploader (limited to only members and they can only upload pics, else is disabled)
Online members within last 24hrs.
Last threads marquee
Limited guest viewing
Forum stats (on footer)
Does your File uploader checks for proper file extension? Cause many times hackers would add a .jpg extension to their their malicious files i.e. evil.php.jpg
Try to disable all those mods and see if problem occurs again.
Regards.
Val