Woke up this morning, logged onto my workstation, realized nothing was behaving like it should.
Windows were tearing, whole screens were acting weird and I could not for the life of me surf the web with ANY browser I had installed. Which wouldn't be as irritating right then and there, if it wasn't for the fact that I needed to log into my online bank-account!
After an hour of aggravation, and another hour of testing with different graphics-drivers (NVIDIA stable/current), I found out my GPU (GeForce GT520) did not play well with the new experimental driver from NVIDIA.
sudo apt-get purge nvidia-current && \
sudo apt-get install nvidia-current
The above command resolved my issue by removing the bleeding-edge nvidia-driver and replacing it with a version-rollback (v319 instead of v331).
After a warm reboot everything worked perfectly! Spotify, Steam, Chromium and Thunderbird all started, worked and rendered like they should.
Dunno if I'll be re-installing the experimental driver any time soon. Time will show.
For now, the stable current-version does it's job.
Who knows, maybe the time is right to replace my NVIDIA GeForce card with a more recent AMD Radeon HD card? I'm quite sure I read somewhere that the Catalyst Linux driver had ironed out most of the major bugs (fullscreen HD crashes / screen tearing / etc.).