I have the same issue using Nvidia (proprietary, tested) driver 331.38 on my HP Envy using Ubuntu 14.04 LTS, kernel 3.13.0-32-generic x86_64.
I also switch to a console using ctrl+alt+f[1-6] and then back to ctrl-alt+f7 and all works for a short time then it happens again.
I have the same issue using Nvidia (proprietary, tested) driver 331.38 on my HP Envy using Ubuntu 14.04 LTS, kernel 3.13.0-32-generic x86_64.
I also switch to a console using ctrl+alt+f[1-6] and then back to ctrl-alt+f7 and all works for a short time then it happens again.