Last night my moodle site run out of disk space. After solving disk problem and restarting my moodle server I faced with "Your session has timed out. Please login again." problem. I googled and found suggestions like:
1. check and fix your permissions in moodledata/session -- set it to 0777
2. delete all session files inside moodledata/session directory
3. check that your hard disk is not full. If you have disk space problem then expand your disk space.
4. delete cookies of your browser
I did all suggestions that were suggested, but it didn't solve my problem. How can I solve this problem?