Long-time fix finder, first-time poster...

Have had and enjoyed Skyrim since November 2011, and it worked flawlessly. Totally vanilla standard install version. No play over the summer, came back to it the other day and the sunlight shadows everwhere (indoors and out) are flickering on/off, total evelopement/disappearing; and only when I look around, move forward, or strafe - but not when I move backwards. Even stranger, when in third-person view, the shadows are stable, but move to where I look, like the lightsource for the shadows is adjusting to the center of my vision around the character.

This doesn't appear to be related to patch 1.5 shadow bugs, as the symptoms are different and the fixes haven't worked for my issue.
I have reset graphics settings to low-high, and returned to defaulted setting many times.
I have a GeForce 9600 card - not much I know, but it's gotten the job done well on all of my Bethesda games.

Cheers