If you are gonna run your ntsc or any xbox in PAL 60 then I would suggest that first you double check it is set up right first.
NTSC peeps - but note this is assuming that your TV will dispaly a PAL signal first - don't blame me if you set it to PAL and get a total black screen and have to reset it back to NTSC "blindly" when you find out your NTSC TV don't display PAL 50/60 at all
Force your xbox to PAL via enigmah say and then go to your ms dash and check that PAL 60 is enabled/YES in the settings to ensure the frame rate don't drop on certain games - Otherwise you could be running some PAL stuff in slower PAL 50
(PAL 60 option only shows up when running in PAL mode or PAL xbox's - Doohhhh you already knew that I presume)
You only need to do this once to ensure that your unleash or evox or whatever dash you using will autoswitch over to the games correct video mode and be fully optimised - ie: PAL 60 where/when needed
Then set your xbox back to ntsc by default via enigmah or whatever
Some games that are LIVE or multi won't always auto-switch to video mode but should still play
You can check the region of ceratin games on ya dash if using avalaunch - highlight the game in ava's menu and press start then go to properties and it will tell ya the region - PAL/NTSC or LIVE=multiregion I think
Soz - some of you will know about this stuff but just pointing out a few things to the others and yes this video mode stuff on xbox is much qwerkier than on PS2 - some TV's I have will boot a NTSC PS2/psx in colour/color via a half decent scart but the same TV will play a ntsc xbox in black & white using a really good fully wired gold plated scart lead - wtf

??
Most UK TV's made in the last 2 years or so though do seem to play ntsc games in colour ok though - just some of the older ones are qwirky especially so on xbox than PS2 consoles
Alas many NTSC TV's don't like PAL signals at all so please for your own sanity try and check first before you end up with a totally black screen after your forced it to PAL modes