Staying logged in

[Obtruse_Man4]

It's been reported to me on my forums that atleast one member has a problem staying logged in.  She'll log in, go to a forum to post, but then will get logged out again.  At first I thought maybe it was cookies, but that doesn't seem to make sense.  It works fine for me, I can log in and post without a problem.  Any ideas?

Here's my site:  hxxp:www.rockbreak.com/~obtruse/forum/index.php [nonactive]