I have experienced this problem under both LMCE and pluto. The problem was caused by a module version mismatch, can't remember which module sorry. The only way I managed to fix the problem was to uninstall all the nvidia packages using apt, then re-install the packages using apt.
When uninstalling the packages make sure you note down the names, so you can reinstall at a later stage.
Another thing you could try is downloading and installing the same version of Nvidia drivers that are shipped with LMCE as this should resolve any module mismatch errors. MAke sure you reboot after installing.
Good luck NOS