Geo cache messing up object ID's/multimattes

[X14Halo]

Say for example I have an object with an object ID. When I render it the multimatte pass comes out fine, but as soon as I bring in a geo cache for the object to animate it, the multimatte passes come out black or corrupt looking...any ideas?

edit: material ID's work fine, so we are going to use that...but figuring out why the object ID's aren't working would still be nice.

[vlado]

I'm not sure what's the problem right away; can you get me a scene or a more specific way to reproduce the problem?

Best regards,
Vlado