Why do some Windows 7 icons looks gritty all of a sudden?

[cornered_fox]

Hello,
all of a sudden after setting a custom refresh rate for my tv, some of my Windows 7 Ultimate icons are looking gritty, on the desktop, in some folders, and in the system tray. I noticed this happened when I set a custom refresh rate of 60.001Hz (I need this for some of my games to work properly). I reverted back to my normal 60Hz and the icons stayed gritty!

 

[cornered_fox]

Never mind, found the answer. Nvidia Control Panel changed colour depth from 32 to 16, that's why everything was looking gritty.