First of all make sure the “remember me” feature is selected. Next line of thinking is that you have a duff cookie. Click from the IE menu Tools>Internet Options>Delete Cookies. From there it is conceivable that you have somehow managed to have your browser not accept cookies from this site, in which case it will be worth having a delve into the IE security settings.
Pete, it is not the fault of us or Key that you are having a problem, but more likely a tech issue with your PC doing something unusual in the way it interacts with the vbulletin software Key uses. Not to mention countless other sites.
BR
Could be so, Outlook Express has gone mental and trying to sort that out has been a problem, the voices in Bombay claim to have sorted out a virus.