Tarq57: If you find out how you did it please let me know.
I downloaded Firefox 3.5.5 a couple of days ago and now I am faced with the same problem.
Cookies enabled and Remember Me is ticked but I have to sign in each time.
At the same time another problem has reared its head.
I think I have all the right boxes ticked but the address bar will not remember any urls I type in it.