Hoi Chumski!
That's strange, is anyone else having this issue?
Possible reasons (shooting from the hip):
1. Running your browser in 'stealth' mode. Also called 'porn' mode, it's where your web browser will not save any history, cookies, etc. The Pub uses a cookie to keep you logged in. If you clear out your cookie cache, then the site won't know who you are.
2. Some application is deleting/removing cookies.
3. Your using a computer that restricts internet browsing and deletes the cookie as soon as it saves (i.e. a public access pc, library pc, work pc, etc)
4. Umm... only 3 ideas?
