Pulled tank and gas is spewing from the vent tube, even though the tank is on its nose.Probably unrelated to the leak you saw before you pulled the tank?
The first time I pulled my tank it was in the winter. It was the last thing I did that day, set the tank
outside, on its nose.
When I returned the next morning a siphon action had started (I think you're supposed to hold
your finger over the vent tube when you turn the tank on its nose to prevent the siphon action
from starting...) and there was a frozen fountain of gas coming out of the vent tube

...
What everyone else is saying about heat and full tanks and the cracked hose you found at
the tee is probably what caused the gas leakage you saw before you pulled the tank...
Daniel Meyer was talking about how important that tee is, and the lines that are hooked to it,
one of the times that I walked past the tech-demo at InZane, so when you fix the cracked hose,
try to hook everything back like it is supposed to be... I think the line on one side of the tee
goes to nothing, it acts as some kind of siphon break, someone will probably say more about it...
-Mike