Widescreen (work-around) fix...
Whenever you change your in game resolution in LockOn, the graphics.cfg file defaults to enter an aspect ratio (AR) of 1.33, regardless of the actual resolution selected in the options. This results in the screen being stretched or "fattened" with widescreen displays and happens anytime you save any setting (not just graphics) in the options section of the game (even if the AR was set correctly before changing an option in game as well).
To prevent the graphics.cfg from getting overwritten every time you go into the options section of the game to make a change, perform the following change in its file attributes:
Right click on the graphics.cfg file and select properties and change the file attributes, by filling in the checkbox for Read-only and Hidden and then hit Ok/Apply.
When changing resolution, select the desired one in game; but also make sure your aspect ratio is set correctly in the file itself, since this cannot be adjusted in game and has to be entered manually thru editing the file in notepad.
Some aspect ratios for common display sizes
4:3 screen; 1600x1200, 1024x768 etc - AR = 1.33
16:10 screen; 1920x1200, 1680x1050 etc - AR = 1.6
16:9 screen; 1920x1080, 1280x720 etc - AR = 1.78
Note: Aspect ratio is the display's width divided by its height in pixels.
Graphics.cfg Widescreen fix
You also can use LOCFG: http://www.3rd-wing.net/LOCFG/LOCFGSetup_beta3.exe which allows you to set the aspect ratio and several things.