Never had that. However, there are bugs that should be fixed, most noticably when logging out. With the exception of, I think, three occasions, I always get taken to an error page that tells me I failed to log out. It occurs regardless of browser.
Mike
The logging out feature definitely seems to be buggy, though I get that mainly in Firefox. It seems to be a cookie bug of either vBulletin, or all current browsers. Not much I can do I don't think. :)