vsync fails with conf.ini specified resolution

[TheFamilyMan]

I can set my IL-2 1946 resolution to 1280x1024 successfully by using the conf.ini file; this is my TFT monitor's native resolution. Most of the time vsync fails as this resolution, but not always. At 1280x960 vsync works nearly every time (it fails very rarely). I enable vsync using the nvidia control panel, of which I'm very familiar. I'm running 2x7800gt (oc'ed) in SLI using forceware 163.71. I've tried later drivers and the nvodngov's but this seems the overall best I've used with my rig. Any advice?

BTW, I use a TIR and tearing ruins the effect and makes the sim unplayable, so I must have vsync. Thanks for reading.