Surfing Forum Logs-me out!

Hi guys

I've had a log-in problem on and off for a while. Quite often when I search a question and see a thread that could give an answer, I get spontaneously logged-out either when I click on that thread to read it or if start to add a reply to the thread and have to log-back in (and find any text I had written gone forever). This only happens if I open a thread. If I just start my own thread without looking at any other, I stay logged-in.

Has anyone had this problem or is it a known issue?

Regards,

Graham

Dell Precision M6700 running Win7, 64bit, SP1 and Trend Worry-Free Business.