The only thing I have to offer is that it isn't an issue with the one being a 64 bit Windows 7 OS. Works fine on my various computers and OS systems.

Was the download for the DPP one where you have to select your OS from a list? I can't remember if it was or not. Any chance you may have selected wrong version or that the link was to the wrong version?

Does it make any difference if you preselect the photos and then start the HDR?