dj, when you make an account for demos, go to CP - View/Edit Member Records, find this member, and choose that he's not allowed to edit his profile - otherwise we can change the password.
About your site, I like compact headers

(although you forgot to modify ubb_forum_summary.cgi per to its instructions). I think your post icons are too big, (taken from ezBoard, right?), yet the new/old/hot post icons are nice

Also, topic tables have 1 empty cell (because you moved the new topic/reply buttons).
Oh, and about this hacker... Did you fix the security problem? If not, if it was from the UBB, check noncgi/BanLists/adminlog.cgi file. If it was from the server (FTP, etc), check your access log (if you don't know check the UBB first, and access log if you can't find any)... The adminlog.cgi file tells you what each admin, with IP, did. So if an account was hijacked, you know you should change all passwords, if an admin is "betraying" you, you should ban him and THEN change the password... Also, after you do that, check that the temporary admin didn't admin his other username - go to View/Edit Member Records, choose advanced search and search only admins. Check the list to see if it's correct.
LD, btw, I dislike mod dropdown (

), but I agree they should completely remove the moderators column
