Problems with Nvidia Drivers in Ubuntu 14.04

i have sual booted machine (Win8.1 and Ubuntu 14.04)

Ubuntu 14.04 has the option to use the Nvidia driver (331.38)
but after installing it, the computer hagns and unresponsive every once in a while
only perssing Alt+Ctrl+F2 than Alt+Ctrl+F6 to go to the shell than back fixes it

i have Nvidia Optimus with Gforce 540MX inside
Using BumbleBee works but makes the computer very slow and low res

everything worked perfectly in ubuntu 13.10 and older with Bumblebee
any ideas?