OK it now will install.
I had not loaded the patch http://www.nvnews.net/vbulletin/showthread.php?t=62021
because I originally installed 8178 without problems prior to the patch issue date. And I had reloaded it several times so I figured that WHATEVER the patch fixed, it did not apply to me.
My bad. After I loaded the patch the install went normally. I still don't understand why, though.