I am having the issue on 10.9.1 while logged in. I have tried other accounts including an admin account, using different groups, different settings, different sharing, and the Category Gallery just hangs. I am getting the same error as Randy. When I check the web traffic it appears that the gallery is finding and loading the category information.
I tried moving or Minimal Gallery apps to the Category Gallery app template in preperation for upgrading to ArcGIS Enterprise 11. I may go ahead with migrating the apps and then upgrade to 11 to see if that fixes the issue.
"Not all those who wander are lost" ~ Tolkien