Cannot reach our new update server from clients

The update server is Mountain Lion and the clients are all Lion. If I reset the update catalogurl to blank, I can get updates from apple.com. When I change the path back to myserver.sprise.com, as suggested in many articles above, I get an error "The software server myserver.sprise.com is not responding."

Can anyone suggest what else to check or setup?

I can ping the server as myserver. The server can get updates from swupdate.apple.com. I've tried naming the server myserver.sprise.com and myserver.local with the same results.