I made a couple of small tweaks to your profile, not sure if it will make a difference or not.
Do you have your browser set to accept cookies? If not, then the boards will not be able to remember you and it will keep making you log back in. Make sure your Norton or McAfee isn't blocking the cookie too.
Try clearing out your browser cache as well. If you visited a long time ago and then came back, the cookie may still be in your cache but not recognizing something, like a new IP address your ISP might be routing through. There are a lot of different reasons this may be happening, but these are the most common