I think I had this, I didn't follow the destructions and set the caliper so the rotor was central instead of left of center (away from the spokes), did an up 2 front and it blow up.
I think this is what has happened to yours.
The topic might still live, i'll go have look.
Back in a mo.
EDIT: Gotcha!
http://www.trials-forum.co.uk/index.php?showtopic=141974&st=0&p=1982682&fromsearch=1&#entry1982682
and i 'popped it back in' with a bloody big hammer and gaz behind it BTW (he's the one talking shit at the bottom of the page)