Followed everything, turned off security, no apps running, uninstalled all previous versions, cleaned out all temp files, registry entries.
Put in AutoCad2011 32-bt disc of the Revit 2011 MEP Suite Pack which included a 32 bit disc, 64 bit disc and Revit.
Installing AutoCad 2011 no problems until I hit the language packs and then this happens:
The powers that be at Autodesk don't seem to look at these forums very often, maybe they are too busy fixing their products???
I had a similiar issue when I originally installed 2009, try copying the disc over to a file on your computer and install from there.