Theres no rhyme or reason - at least to me - on why this occurs.

I think there was a thread on this a while back but I cant seem to find it again.

I will sign/log in and surf the forums, post replies etc. I can go away to refill my coffee and come back and continue on. Then there are other times when I am reading a thread and move on to another and it asks me to re-sign/re-log in again. This also happens often after I finish typing a reply to a thread as well.

Anyone else have this problem?