But I believe the forum software requires a specific cookie to be set so that the login can be remembered for a certain number of days. If an application like McAfee LiveSafe or some other is heuristically watching for and clearing the cookie, that might explain why it's happening in different web browsers and at seemingly odd times. Most of the anti-malware apps have a way to exclude or whitelist a site from those sorts of operations. Might at least be worth looking into.
Otherwise, I got nothin'...
