The actor behind the mask of Darth Vader has been banned from the Star Wars Celebration V convention and any other Lucasfilm-associated events, he said on his site:
"It is with regret that I have been informed by my friends at C2 Ventures, Ben and Phillip, that I am not to be invited to C5 this year or any other Lucas Film associated events. After enquiring, the only thing I have been told is that I have 'burnt too many bridges between Lucas Film and myself' - no other reason given...I have also been advised by the promoter of Paris Manga in September that LFL (Lucas Film Limited) have requested no photo opportunities with the 501 Squadron, even though I am commander in chief of the 501"
There is a lot of speculation online about what "burnt too many bridges" means, but no one seems to know and Lucas and Prowse aren't saying. If we find out more, we'll let you know.