i updated my itunes and i got a new version of qt...6.4?

I'd wait a little while and let the cutting-edge guys try it out. Remember OS-10.2.8?

see what www.macfixit.com has to say about it.

If you're using FCP or FCE wait until Apple approves it for your editing software.

FCP is the only Apple product. I believe it was needed for the new version of iTunes (also PC compatible). They didn't want to delay the release because of any issues with FCP. It, or another version (included in 10.3 due next week) will be made available soon for FCP. It may just need to be certified.

The QuickTime 6 MPEG-2 Playback Component provides users with the ability to import and play back MPEG-2 content within QuickTime 6 and Compressor (included with DVD Studio Pro 2 and Final Cut Pro 4).

This MPEG-2 Playback Component update provides compatibility with QuickTime 6.4 and is strongly recommended for all users of QuickTime 6 and Compressor.

there have been a few reports of problems from people updating to 6.4. i'd advise either waiting or being fully backed up before moving to 6.4 so you can move back down if you need to...