Yesterday, I pulled the tap and got this:

What the hell? The keg was working fine two days ago. What changed? Oh, I know. I defrosted the kegerator freeing the thermostat from being incased in ice. That could be it? Has to be, it is the only thing that changed.
I took the keg out and discovered frost on the side of the keg, and most of the beer inside was frozen solid. I shook the keg and heard the distinctive "thunk" of the frozen beer hitting the side of the keg. $hit.. What do I do now? ..I decided to untap the keg shut off the Co2, and leave the keg out overnight to defrost. Then another night. And another. Could not believe it took 3 days to defrost.
I wanted to test it before I went through the trouble of putting the keg back in and setting the Co2, so I tapped the keg while it was still out of the kegerator using an old pump-style tap (think frat party).. Beer flowed. Next came the all important taste-test. Tastes fine and major crisis averted. Life can go on.
So what happened? After I cleaned the kegerator, I left the thermostat control on MAX. Whoops.
Not frozen no more:

In case you are wondering: Those brown speckles on the head of the beer (Killian's Irish Red) is a mixture of Brown Sugar, Nutmeg, and Cinnamon.
Edited by brian12566 - 12/14/12 at 4:50am