Why won't Office 2011 install on Snow Leopard?
I tried to answer this the day after I posted the question, but my in-law's Internet connection wasn't being cooperative.

I was only able to install Office after we wiped the machine and reinstalled Snow Leopard.  I have no idea what the actual problem was.  The machine was really slow anyway and now it's running like new.

I guess the old rule about Microsoft Windows extends to MS Office for Mac:  format and reinstall.  :(