It was on the correct post (since I expect that question). I went into the garage as I was heading to work and saw beer on the floor, then looked in the fridge and saw that beer had been seeping from the top of the QD. I disconnected and turned off gas (simply because I didn't have time to troubleshoot). When I got home, I was relieved to see that I still had some beer in the keg and gas in the canister, so it wasn't a total disaster.
The night before, I had taken apart the quick disconnect and cleaned it before reassembling and attaching. I'm embarrassed to say I had not cleaned the QD before--I only recently realized it could be disassembled. I'm guessing I reassembled it incorrectly--too tight? too loose? I have another new beer line QD in pristine packaging that I'll swap in.
So... when I clean and reassemble this QD... what am I looking for? How do I ensure it won't leak?