I've been having cookie problems as well, and think I found and fixed the problem last night. The problem occurs when the "get_cookie" subroutine is called more than once by a single script. This problem gave me **** with the private message hack. For a little more info, and how to fix the problem, check out:
http://www.scriptkeeper.com/ubb/Forum14/HTML/004088.html W.T.F?! I cant say H E L L on here?