We stumbled upon a rather ugly looking issue affecting Revit 2011 realistic views after applying the latest Mac OS X update.
After applying the update to the Mac, Revit 2011's new realistic view materials look all funny (a very technical term) when you are running a Windows OS with Parallels 5. Here is what you get (with the basic sample project in 2011):
We've confirmed that this issue happens when you have updated your mac to version 10.6.3 with the latest version of Parallels 5 (5.0.9344.558741) and you have hardware acceleration enabled (on the OS and Revit).
We've talked to the team over at Parallels and they have informed us that this issue is planned to be addressed in the next update of Parallels Desktop 5.
If you have already updated your OS and are seeing this, I don't have a good solution till Parallels releases their update. I have not found a way to roll back a Mac OS X update, though I am not a Mac expert by any means.