For about a year now (don't know the exact driver version where the problem started) I'm seeing transient artefacts and noise on my screen after some usage. How long it takes to start varies (usually not right after boot) but only rebooting fixes the issue. This is what it looks like:
Sometimes it's just a glitch that is visible for less than a second, sometimes the screen remains like this until the app needs to redraw itself. Also, after a while, some of the fonts get garbled permanently. Not all of them, but the ones that do, will remain like that (i.e. even in new app instances, e.g. when it's the menu font or the console font) until the driver/X server is restarted.
I'm using a laptop with an nvidia GT218M [NVS 3100M] (rev a2). I have just upgraded to 15.04, but the issue started over a year (so at least two OS revisions) ago.
Anyone knows what may cause it and/or how to fix it?