Did you uninstall everything youtube related prior to installing the new app?
Have you logged on to your youtube account?
While on Stock ROM...
The process to get 2.2 Youtube onto the phone was to get rid of some of the original /system/app files, and then install a custom 'signed_youtube...' apk. Due to this, when I would hit the "force close" situation, I'd just go to Settings -> Appliations -> Manage .. and then uninstall Youtube. I then kept a handy apk on the SDCard that I could quickly reinstall. At that point, I would then be able to login to my youtube account, and I'd be able to load videos... for some "random" period of time... Inevitably, it would eventually FC again, and would be stuck in this state until I did the uninstall/reinstall steps.
there may be easier ways of resolving the issue.. but, this is what worked for me.
As for now that I'm on JT's Clean ROM, I still have yet to see the FC's start... when/if it does happen, I'm not sure what I'd do to try and resolve........
Well.... as I'm typing this, I try to launch Youtube, and I get the force close....
Guess we're now both in the same boat...