I log in to a certain site on one pc OK, but I have a problem with my win98 pc at home. I log in and the site successfully returns the main page with my username displayed. When I navigate to another page or refresh, my username is lost (guest is displayed so I can't enter new threads) although I remain logged in according to the logged in users list.

I have cookies enabled.
Is there some setting that was corrupted and needs fixing?