I had the same issue but with Autocad 2008.
The solution I found was getting the XML6 SP1 version from microsoft's download site (
http://www.microsoft.com/downloads/d...isplaylang=en). I then replaced the msxml6.msi file with the one I download (it has to be renamed from msxml6_x86.msi to msxml6.msi). Ran the install and it worked fine.
P.S. I signed up just to post this for future reference for other people.