hmm...that's strange about the combining locking up maya...don't know really how to fix that...try running the cleanup function on your mesh and optimize your scene file...see if that helps a bit.

What you might try as another option though is to just group the objects together (ctrl+g) and then rotate the entire group. They'll still be different pieces of geometry and can be selected separately in case u want to orient each individual piece by itself, but when u select the group (hit the up arrow when one of the items is selected) you'll be able to roate them all as if they were combined.