MacBook – OS X Video Driver corruption

I have a mid-2010 Macbook Pro with 10.9.4. I've been using it with a Seiki 39" 4K TV as a monitor for about a month now with no problems. (This is using an UltraAV MDP to HDMI Active Adapter cable.) For the first time yesterday I selected "1080p" as the resolution in Display Preferences to see what it looked like. Immediately after going to 1080p resolution, the list of resolutions went blank. I could click (or option-click) on the scaled circle, and there would be a delay of a few seconds, then I'd see a list of resolutions flash up, and then go away. Based on what I later figured out, I think if I had tried to click one of those selections when they flashed up, I would have gotten out of 1080p mode. But I did something else, trying to reset the display preferences to a normal state. (I don't remember what exactly)

From then on, the Mac seems to think it's talking to a dumb TV. It only lets me select 1080p, 720p, and two other resolutions. Additionally I get a slider for "Underscan" which tells me it thinks it's talking to a TV in some sort of "TV-mode". I don't see the full set of resolutions going up to 4k that I was seeing before. Here is what I've tried with no joy:

• reinstall jumbo update for 10.9.4 (no help)
• updating firmware on the TV
• reseting TV to factory standard
• logging in as another user (still see 1080p)
• Resetting the PRAM
• logging in in Safe Mode (this works!)

I'd like to remove/reset/review all the non-user files that are different or new since the base OS was installed (counting updates).

The only other thing I can think of is to reinstall the whole machine.

Any ideas short of that?

Update:
Option-clicking the "Scaled" choice enabled about 10 additional choices, which are all smaller than 1080p. But still no 4k choices, and I still get a slider for Underscan, so it's still in 1080p mode.

I tried the SwitchResX app, and it might have had a way to help, but I wasn't able to figure out how to do what I wanted. The normal default operations didn't seem to allow the resolution I wanted.