While browsing around the forum, you are logged out for no reason and have to keep logging back in again.
Things to try:
- exit the forum
- close all browser windows bar one
- go to Tools > Internet Options > Delete Cookies > Delete Files > OK
- close the browser
- reboot machine
- open browser
- log in again
This can be also be caused by the cookie settings in your browser, firewall or other privacy software.
Try turning these off one at a time and see if the error stops occurring. If it continues, please post a message below.