The next version of the Mac OS X operating system, Mountain Lion, is expected any day now and Autodesk just released a technical solution regarding support for this new OS:
The short version is that no AutoCAD for Mac or AutoCAD LT for Mac products are currently supported on Mountain Lion however they are actively working on adding that support. As explained in the solution, there will be beta programs announced for service packs for AutoCAD 2012 for Mac and AutoCAD 2013 for Mac that will add support for Mountain Lion. Until a service pack is available, they recommend NOT installing Mac OS X 10.8 on any systems running AutoCAD 2013 for Mac, AutoCAD 2012 for Mac, AutoCAD LT 2013 for Mac, or AutoCAD LT 2012 for Mac.
I know I've said this before but I tend to be cautious when upgrading operating systems anyway. Two of my daily-use machines are Macs and I just can't afford the risk of disrupting my workflow because some critical applications are not yet supported or because the OS fundamentally changed something that affects how I work (I still have a Snow Leopard partition on one machine for this very reason). Even if AutoCAD for Mac and AutoCAD LT for Mac were fully supported on the same day that Mountain Lion is released, my personal recommendation would still be to wait a bit before upgrading.
There is a reason it's called the "bleeding edge".