3D Effect - Extrude and Bevel not working for particular shape, but fine on almost identical shape

Hi All,

I'm trying to do a 3D extrude and bevel on some images, however it's not work for this particular shape. I've managed to do several extrudes on different images today all working fine, but theres a couple of images it's just not working on.

The one i'm currently doing is this one:

but it's worked fine on this one:

They are all set up the same way and i'm trying the same and different settings. I've tried going back a version in Illustrator incase it was a wierd bug or something, but I'm not having much luck. 

Does anyone else have any ideas?