Guys/Gals as a reference please find below the current list of games that require your console to be set for 60Hz
Changing your settings is quick and easy, just follow these steps:
Some people have reported not seeing any PAL options when using the above method, in which case they need to flick the TV mode selector on the video cable from "HDTV" to "TV". The console will then restart in standard definition. You can then navigate to the System blade and follow the above steps and change from PAL-50 to PAL-60.
When this is done, flick the selector back to "HDTV" on the video card and you're good to go!
Also there is an official support thread posted in the support section of www.xbox.com
We will be adding to this list as more games are confirmed as being PAL-60 only.
Please note: Some older TV sets do not support PAL-60. If you are in doubt consult your TV manufacturer.