ok... i had not restarted itunes since it had updated
i had trouble adding videos as posted in other threads, trying to fix this problem i resarted itunes
after resarting itunes it then gave me the above message about not supporting quicktime... grrr
I HAD JUST WATCHED VIDEOS LASTNIGHT!!! i knew something wasn't right here as i know itunes updated days ago
i then rebooted my imac, opened itunes and tried again to play a video and IT WORKED!!
it seems that there might be a few glitches in version 11
hopefully if anyone else has gone through the same process and had the same problem a reboot will be the fix
Have a nice life