It is becausze the script has not been updated to the latest string (VB 3.5+) when you sned the server a logout command......
It should be this http://www.oldversion.com/talk/login...44a19ffa0f34e5 (logout hash @ the end)
Instead of the old way
http://www.oldversion.com/talk/login...=logout&u=1566
(I've seen it on other 3.5 sites that didnt update everything properly)