Passwords / Login's etc

I know there are websites that force the browser not to save say the password of the user though it may remember the username but the sites i use have not tried to make this happen. I allow the browser to save my details because no one but me uses this pc.

Recently and I'm talking about the last 2 / 3 day's here when opening Firefox the xbox.com site has started logging in another account i had signed up there one which i had deleted all details from within the browser. I'd actually re signed up so saved the new details. For example i just refreshed all my tabs and was signed out completely, no log in details at all in fact now i think about it, however i also just turned on the 360 so I'm now thinking maybe this is connected.

However something similar happens with Bebo. I changed my username deleted the old saved details but FF refuses to bring up the new details instead showing up the old username, It really is bugging me because i like things to work a certain way, and it's not doing it !

Also, and this seems to be an occasional thing, i have all my windows set to fill up only a portion of the screen and not maximised and until now this has been working fine but sometimes I'll click to open my music and it opens maximised, that's just one example but the question is what is causing this ?

As per usual all the usual checks have been done and the whole computer is, as far as i am concerned, completely free of shiteware.

Thanks in advance for any help / advice : )