Originally Posted by benwah
I did disable optimus in the BIOS and set the graphic adapter to nvidia. That is also the default configuration for Lenovo t420s, but I can confirm that Optimus is disabled and the adapter is nvidia.
can you read http://www.nvnews.net/vbulletin/showthread.php?t=46678
and generate a good report with the debug ( -logverbose 6 ) info as instructed after the issue appears ?