Any Ideas what could be causing this?

It is probably John restarting the login server

Nah, the LS restarting does not effect his routeable hostnames. That, and I haven't restarted LS since 2 nights go after fixing up the opcodes.

I get this all the time, too - and it's usually MY isp freaking out and dropping a critical router or some crap and DNS just hasn't re-routed me through the interwebs before my World wants to check it's heartbeat.

Error 11004: Unable to get the hostname. - Does the IP it's trying to connect to have a hostname?
Error 10053: Client drops the connection due to errors. - Possible hardware issue (bad cable, bad ethernet card, noisy phone line)?

The 10053 is what you normally see when the LoginServer restarts.