Had this problem yesterday with a new iMac (iMac10,1).
I had an old Windows XP SP3 image with all the applications etc I wanted in Windows. I applied the image to a Boot Camp partition, booted Windows without any problems.
Now I wanted to install the Boot Camp drivers from the Snow Leopard DVD, I launched the installation, but it failed immediately with a message saying something like "a problem occurred, please try again later".
The event log said "msiinstaller error code 11708", which gave me nothing.
Then I launched the BootCamp.msi (in /Boot Camp/Drivers/Apple) with "msiexec /i BootCamp.msi /l* c:\bc.log". In the log file I found that a function called GETINTELGRXID failed with exit code 3.
I think this is supposed to get which kind of Intel graphics card it is in the machine, but since it's an Nvidia card in this iMac I thought it didn't matter if that function ran or not.
So next thing to do was editing the msi with Orca and delete all entries that contained "GETINTELGRXID" (I think I found it in two places). When that was done, I just saved the msi and launched it with the command above, and it worked! Now I have an iMac that have a fully working Boot Camp install!