Are u using any plugins? Hopefully u r not using replica, which won't support grps.  If u can I would also upgrade vid drivers altho...doesn't necessarily sound like an issue. Hard to say w/ that info. There have been some nasty limitaions particularly in polygon support in earlier ati drivers. Try double clicking on the replicator instead and setting things from the interface to make sure they r set correctly rather than dragndrop. Also remember to constantly clear unused master shaders and objects...they really can accumulate.

No need to think outside the box....
    Just make it invisible.