Dude, which version are you using? 2.0? 2.0.1? and which database? mysql?
I downloaded JForum-2.0.1.zip from sourceforge and didnt' found this problem. If possible, can you please try reinstalling jforum and see if it works then? ( removing the entire directory, or putting into another one, instead of replacing files.. )..
Rafael [originally posted on jforum.net by Rafael Steil]