windows xp install problem ("failed to set permissions on the installed files...")

I have installed PG on Windows XP successfully several times, but now I
have one machine on which the install
fails with an error message: "Failed to set permissions on the installed
files. Please see the logfile at ..." . The log file in question does
not look very useful. It has lines of the type:
  processed dir: F:\PostgreSQL\8.1\xyz
  processed file: F:\PostgreSQL\8.1\xyz\xyz.xyz
with the last line saying "The data is invalid."

I tried both v.8.0.4 and v.8.1.1 and I get the same message from both. I
am using the MSI installer for both. The computer is running Windows XP
Professional. I am installing onto an NTFS-formatted drive, which I
understand is a requirement. I am running the install as the local
Administrator.

Any ideas on what to look for. Any special permissions I need to set
outside of the install or before the install?

Thanks!

George