I think I found the problem. Did you by chance try setting TESV.exe compatibility mode to Windows 98, as suggested elsewhere for performance? Check the properties on that file, make sure "compatibility mode" is unchecked. Maybe check SkyrimLauncher.exe just in case as well. This got me - even though I created a shortcut, and set compatibility mode on the shortcut, it actually applied to the EXE. Also, I deleted (!) the exe and re-acquired it via steam, but this did *not* remove compatibility mode! It's some kind of dark juju.
