Usually when I suffer the dreaded writer's block, it's because I have too much other stuff on my mind. Since I work at home now, I've learned to do most my writing when everyone is either in bed or gone.
That said, I will get away from the computer for a little while -- take a walk, do the dishes, something mindless. But only for a short time.
Then, do like the rest have mentioned already. Do an outline, write a couple grafs to rearrange later. Transcribe your notes. It will start clicking, it just takes a little time sometimes. Just try not to stress over it, that will usually make it worse.