Did some testing and this problem is related to some people not being able to create Buy&Sell posts.
The solution -
1. Manually delete all ClubSNAP-related cookies from IE/Mozilla/Opera - there may be a few depending on where you entered the forum (eg
www.clubsnap.org,
www.clubsnap.com, forums.clubsnap.org, forums.clubsnap.com)
2. Restart your browser.
This logout issue may potentially affect quite a number of members as we (today) changed the handling of cookies on the site.
Once you relogin using the new cookies, you should not encounter the logout problem again.