I've seen a few posts mentioning screen flicker, but since ICS, the screen flickering in the YouTube app is really bad. At times, when i first open it, the screen flickers and tears for ages.
Also, often when I interact with the app or use the volume buttons, the whole screen goes black, except for the video.
Surely I'm not alone with these issues, am I?
I don't have a concrete solution to your problem but I can tell you that I have no such problem after the update to ICS.
I suggest that you either try uninstalling You Tube updates vai Settings and then update or remove the app altogether and then reinstall.
I performed a Factory Reset and "erase everything" on Saturday, but I still get this problem sporadically - although nowhere near as often as before.
I have the same problem .Youtube and other tubes ....flicker all the time!! I hope for a solution to the upcoming update (for Greece) ''release5'' .