Looking at the vB support board it appears that there is a problem with IE 6 that causes corrupted cookies on occasion and this leads to the problem of not being able to log out. I have installed a add on to the bulletin board that should allow you to remove any board related cookies without going into the browser preferences:

http://www.flyertalk.com/forum/mycookies.php

If you use this or the your browser preferences to delete all of your FT cookies you should be logged out. Please post how the above link works for you if you give it a try. Hopefully there is a patch for this in the future, but I am not sure if that will happen if the cause really has to do with IE 6 corrupting cookies. Thanks,

--Tim