Severe bug that does not allow me to play on my own server

My client immediately crashes when I try to join a locally hosted server.(ie my own)
I have tried many force updates, and reinstalling the vanilla server software each time. But it does not work still. This map was created it 1.3, so I am not sure if that is the problem instead.

iPwnTNT lost connection: disconnect.genericreason

If someone has any fix to this, then please help me. Otherwise, that leaves me prone to griefers/trollers seeing as I cannot administrate my own server.

Steps:
loaded old world from 1.3 bukkit
download 1.4 vanilla server
run server nogui
login using localhost