Remember me uses cookies, but also gets reset if your ip address changes or our server connection is reset, if the number of log ons exceeds a certain number the person logged on for longest is logged out and finally it times out after a certain number of days anyway. basically our system is set to be more security conscious on this than most other sites, I don't know why and I can't change it.
This means multiple things can mean it forgets your connection.
I was 'logged out' several times in succession a week or so ago, for example.
Neil