When you mentioned V-sync being forced on, is this per your Nvidia control panel? I haven't looked in my panel for quite awhile, but is there an off/on/force on? If that's the case you might try just leaving it at on at see what happens. If that doesn't work I'd send your dxdiag to skuzzy and he should be able to help you out.
-edit- here is a copy paste of how to go about sending your dxdiag to skuzzy.
"First, the email address is: support@hitechcreations.com
Next, when asking for help with problems, it can save you some time if you include the output from the DXDIAG utility with your email. You can attach the file (preferred) or imbed it in the email.
Here are the steps to do this:
1) Go to "Start" from the Windows desktop
2) Select "Run" from the pop up menu
3) In the Run dialog box, type DXDIAG and press <ENTER>
4) After a few seconds the DXDIAG utility will be ready (the progress indicator in the lower left corner will disappear).
5) Run the video and sound diagnostics (Select the Display and Sound tabs to do this).
6) Press the "Save All Information" button
7) This will save the DXDIAG data to a file of your choice
Cool Once you have done this, simply email the file to me and I can look for any issues your system might have.
Be sure to include your game ID and/or login ID with the email and a good explanation of the problem as you see it.
We cannot see your computer screen and rely on you to give us as much information as possible about it so we can try to help."
On an aside note, he has mentioned in threads before that if you send the email during business hours and not on the weekend; That he should reply within 24 hours, and if no reply is givin within that time frame to assume that he did not receive your email for whatever reason.