This is a known fault and BMW changed the design, basically the original design is not good enough, they brake/fall off again if you fix them anyway.
See here:
http://www.mini2.com/forum/2nd-gen-f...unclipped.html
here:
http://www.mini2.com/forum/2nd-gen-f...-my-s-due.html
and here:
http://www.mini2.com/forum/2nd-gen-f...rch-trims.html
Some in the news/reviews section too.