Tim, did you get a chance to see if that helped? They're not quite sure how this could be happening over at vB... I cleared my cookies and things work fine for me again. Hope it's the same with you two.
Wolf, the way it should work is, when you click "log out" you should get taken to a page that says "all cookies cleared" with two links: return to the page you were viewing, or go to forum index. Your username will still be on the top right of that screen. But as soon as you link away, your username should be gone.
Gin, no reason to log out really, if you're the only one on your machines. The system automatically logs you out (or should) after an hour of no activity.