Illustrator CS5 (Win7) – Problems when grouping elements and using Isolation mode

Is there a difference in how grouping elements and using isolation mode works in Illustrator CS5 in Mac and Windows?
I’ve tried it in Windows and the isolation mode only partly works - some element doesn’t group together and other objects (the ones not selected) doesn’t fade when I try to build larger groups (with more than two child groups in one parent group).
I’ll post more details when/if needed.

All help is appreciated.

Kind Regards
Bertil