SOLVED. I was having a DNS problem. This finally occurred to me when I was also having trouble reaching certain web sites. I was able to see that it was looking to my home router for DNS. I could not figure out how to change that - but I have a back up 3G connection. I tried that and voila, I could download and install apps.

I have a home DLink router that seems to have a DNS issue with the n810 in some cases. This is something I'll have to deal with in the long run, but in the short run I've got the features I need for my trip.

Thanks for the help.