This question is clearly realted to this one.

However, I tried the suggested approaches and neither of them worked.

Let me explain what happend:
I'm using an Asus notebook with an integrated NVIDIA GPU. However, I've only been using the Intel graphics and it worked fine. I needed the NVIDIA driver for CUDA, so I installed the matching driver from the NVIDIA website.
Afterwards, I could not log in ubuntu with a GUI, but only in text mode.
I then uninstalled all NVIDIA packages. However, I think that I broke something, because I have the same black boxes around all windows, as described in the referenced question.

closed as off-topic by bain, Jacob Vlijm, Luis Alvarado Jul 24 '14 at 21:54

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Bug reports and problems specific to development version of Ubuntu should be reported on Launchpad so that developers can see, track and fix these issues." – bain, Jacob Vlijm, Luis Alvarado
If this question can be reworded to fit the rules in the help center, please edit the question.