I had previously been able to run Skyrim at low-resolutions as well, though that game suddenly crashes every time I try to load any of my savegames... Haven't had time to mess with that though, so it's probably unrelated to the driver problem(s)... It's been a fun couple of weeks :-P
Did you uninstall or deactivate a mod? I had the texture pack installed, and I found loading a savegame that had the texture pack installed caused the game to crash if the texture pack had been deactivated.
Ya know... I didn't, but now that I think about it there was a night about a month ago now where Steam was acting all wonky and I was losing connection to the servers every five minutes. And during that time I tried to start Skyrim and it threw up some kind of error and I think it said it was deactivating a mod... hrm... I'll have to try messing with stuff and see if I can find the mod in question. (thanks to mod manager and steam workshop I've got like 20 of them going :-P)
Thanks for the suggestion :)
EDIT: Update - As it turns out, it wasn't exactly that a mod had been deactivated or deleted. It seems like one of the mods I was subscribed to no longer existed and was throwing an error every time Steam tried to sync it... I simply removed it from my 'subscribed' list via the Workshop and Skyrim was back to normal. :)
The mod was suppsed to be some sort of Zelda themed set of items/weapons if I remember correctly. It was called 'Skyrule'... so it must have been removed or renamed or something in the time since I originally subscribed to it.
Either way, mystery solved! :) Thanks again for the suggestion.