So I kegged a brown ale(first time kegging) all went well had a party beer poured perfectly and tasted great might I add.... Any ways today I poured me a glass but noticed a lot of foam so assumed I was out of beer (which I was hoping for so I could keg a stout that's ready) so I shut of co2 tank closed the valve and removed all lines, then released the pressure and opened the top to find roughly half a gallon of brew partially frozen more like a slush if you will. So I am sanitizing the keg but not too sure if I should keg the stout and have to dump it later on.. my concern is that in the same kegarator where I have the keg I have plenty of beer in bottles and none are frozen so don't think temperature is the issue, also keg is upright and never been shaken or fallen over.... Anyone else had the same issue? Thanks in advance