Thank you, paulroberthill, for the installer log.
I think I get an idea on what's happening. The cause should be related to UAC and Administrators rights. Antivirus software seems unrelated.
I uploaded a tentative update version "mobihandler-1-1-1097-setup.msi" on the same page:
http://cid-88858bc052aea782.office.l...ic/MobiHandler
Mike4672, paulroberthill, and others who were unable to install on 64 bit OS, can you try 1.1.1097 and report back, please?