If everything was fine then it started blowing empty with half a keg left my initial guess would be that the pickup tube INSIDE the keg is spit half way down. IF this is the case you won't be able to fix it on your own and would need to return the keg to your dealer for replacement.
Semper Fi,
The Gunns
"Beer is proof that god loves us and wants us to be happy" - Benjamin Franklin
Im a
MicroMatic Beer Fanatic! Are you?