If Poser couldn't find the OBJ, it would tell you, then crash. :) That's what the Windows version does, anyway. Groups will disappear when their names don't match the references in the CR2 exactly, down to letter case. These wouldn't normally get changed during remapping, but maybe you accidentally ticked the wrong options when saving the model from UVmapper? I'm not familiar with the Mac environment, but why would you need MacConverter?