Maybe you've accidentally made some objects hidden. In the properties panel, are there any objects that have lighter text? That's how Carrara shows you something is hidden in 3D view and/or just plain hidden from all (i.e. won't render, just hiding something in 3D view will just hide it from the assemble room, it'll still render). with the above in mind, have you tried doing a test render? Is the room still hidden? And were the objects in these groups primitives or Spline/Vertex objects? I'm using Mac OS X (10.2.8) with C3 and have had no problems, esp like the one you describe. It could be that the objects could've been moved accidentally. htp, if not, some screen captures of your scene would be helpful. If you run Grab (the screen capture utility in Mac OS X) and then click on the dock for Carrara, you can control-tab over to Grab and still have the Carrara window "below" grab. You can do a selection capture.