Warning: session_commit() [function.session-commit]: write failed: No space left on device (28) in /home/username/ public_html/CMS/Class/auth.php on line 238
Warning: session_commit() [function.session-commit]: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in /home/username/public_html/CMS/Class/auth.php on line 238
This causes of warning message to be generated for php unable to write session data as web server has run out of space So that the query commands cannot be executed. Its necessary to check your occupied disk space using df command with -h.
Clear your tmp directory and refresh of the browser page
I assume that the web hosting has set space for your account which you have exceeded, clean unwanted files from there or contact to hosting provider to fix this Warning Messages.