Looks like YouTube got the boot by the iPhone Dev Team in the jailbroken version of the new iPhone OS 3.0. Due to the new features in YouTube (sign in, rate, comment, etc…), Apple has redesigned the YouTube application for the iPhone. Somewhere in that redesign, a change occurred which led to the application being disfunctional in the jailbroken version of the 3.0 firmware. see more after the fold.
The iPhone Dev Team will probably release an updated version in the future which leaves YouTube intact, but for now, you've gotta choose: Cydia or YouTube?
Let us know in the comments if YouTube is working for you.
Vote here, over 300 votes and counting.
Update: It appears that the majority of users are not having a problem with YouTube.
In the mean timem the iPhone Dev Team released redsn0w – a universal iPhone 3.0 jailbreaking tool for Windows and Mac, read more: