I’ve been having trouble with the Nvidia drivers for quite some time now – a year at least. Every now and then after updating packages via the
Software Updater (I haven’t kept track of which packages exactly caused problems) the system would keep working until the next reboot and then things would get ugly. The login manager appears in very low screen resolution, things are pixelated and when I try to log in, everything freezes. This happened on 12.04 – which I ran quite a while before upgrading to 14.10 – and guess what? Same problems on 14.10 as well.
There are a lot of people having these or similar issues and there are a lot of confirmed bug reports on this. For instance this on launchpad. Fixing these issues seem not to be trivial, I believe the drivers being proprietary does not help. Anyway, time for me say to goodbye to Nvidia drivers. After many not-so-well-spent hours of repeatedly getting my computer back to run, this is it.