Comment 4 for bug 1401350

Been using nvidia-331 (proprietary, tested) prior to updating drivers without problems. After this recent update, on restart Einstein@Home reported "No GPU Available" to do GPU tasks (they were CUDA work packets) and Blender reported me not having any CUDA or OpenCL devices available. I might also had an AMD OpenCL ICD installed which enabled me to see my CPU as on OpenCL device; now Blender doesn't even detect that.

Rolled back to legacy nvidia-304 (proprietary, tested) and uninstalled non-nvidia OpenCL ICD related items to get my CUDA/OpenCL working.

As a test, I then upgraded back to nvidia-331-updates and ended up with the same "no gpu available' / no OpenCL device detected. It is from here, while changing driver to nvidia-331 (proprietary tested) that, during the installation towards the last 1/4 or so I get a "System Problem Detected" which has led me here.

Summary:

nvidia-331 (p/t) before package updates - all OK and working (may or may not have had an AMD OpenCL package installed - only nvidia cards and intel CPU in system)
nvidia-331 (p/t) after updates - no CUDA/no OpenCL
(random nvidia OpenCL ICD package addition/removal, I can't recall)
nvidia-304 (p/t) CUDA/OpenCL working again
nvidia-331-updates (p) no CUDA/no Opencl
trying nvidia-331 (p/t) results in "System Problem Detected (this issue" and doesn't install fully -> property page shows me as still running nvidia-331-updates

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On an unrelated note, I can't install different video card drivers in Synaptic -> Repositories -> Additional Drivers page, it gets stuck at ~10%. It's the exact looking property panel that is in Dash -> System Settings -> Software & Updates. Maybe the panel's waiting for Synaptic to close (to release the lock on the package list?).