I'm running Ubuntu 14.04.1 LTS on a Asus A53SV with Nvidia 540M and Intel Sandy Bridge i7. I've installed nvidia-331 proprietary driver and also the Intel graphics official driver.
After the last graphics update, when I switch to nvidia trough prime, the low graphics mode screen appears, and then I have to switch back to intel manually.
I've purged and installed again all nvidia packages, and the issue still remains. Is there a way to fix this? maybe a rollback of the update.
08/14/2014 Update: I tried to purge all nvidia package (removing them), rebooting, and them re-install them again, then reboot again. Did not work!.
Note: I think the cause of this problem rely on intel-graphics. Maybe nvidia-prime doesn't know the existing of this new intel driver.
08/15/2014 Update I stumble upon this page than showed me how to remove the intel graphics driver
sudo apt-get purge intel-linux-graphics-installer && sudo apt-get autoremove
Then I rebooted, and nothing...
So I'll just re-install Ubuntu when I have the time.