Have you got an Nvidia card and have you made any custom 4:3 resolutions? My FOV also seemed screwed up until i removed a custom resolution i had made for some games, that don't play nice with widescreen through Nvidia control panel. The most puzzling thing about the whole issue was, i never applied the resolution to DKS or even my desktop during the time i tried to play the game and encountered the problem.
I do have nvidia (gtx 280) but I do not have any custom resolutions, and I have only one monitor. I use 1920*1200 everywhere.
And since the patch, FOV is screwed up.
Hopefully Larian folks will be able to fix it soon.
