One site of 500+ is blank on the site and the dashboard. Have been through settings in network admin comparing this site to another and all seem to be the same. Since I can't get to the dashboard I can disable individual plugins. Deactivating all network level plugins did not help.
Default theme was changed, in config, to Suffusion a couple of versions ago, and since it works on all other sites I don't suspect this is the problem. Something related to 3.8 upgrade because that is all that changed.
I suspect it must be an individual plugin on that site, but need a way to access and disable.