Freewheel sprocket locking up I was just out riding my bike. Its nothing fancy, just a €300 single-speed with with a flip-flop hub. I usually ride the freewheel side. Today it made some weird noises and decided to lock up / be a fixed gear and threw me off the bike. 

So now the freewheel sprocket is behaving like a fixed gear. Is the sprocket completely broken or is there any way to fix it?
Freewheels do require lubrication sometimes.

I suspect that if you drip some oil (I've used air tool oil, which is pretty light, but anything will be OK) in there with the bike tilted so the is freewheel up the pawls with become unstuck and it will work fine.

In my experience it won't take much oil or time, it should free right up if lubrication actually is the issue.