I've had that bug too, in Silithus. I went to the flightmaster and got on
the gryphon but it didn't take off. Instead I could move around like normal.
I didn't do much experiencing with it, since on my way up to the
flightmaster I was attacked by a hunter 4-5 lvls higher than me and I just
wanted to get out of there (I got out of combat only 1-2 seconds before
talking to the flightmaster, maybe that had something to do with it?).
Anyway, I logged out and in again and found myself on the gryphon, flying
away from Cenarion Hold. The rest of the trip was a bit strange too. After
flying over the Gadgetzan FP (I was going to Theramore) I started flying
very low, and eventually into the ground and underneath it. Then, when
reaching Steamwheedle I was sent back to Gadgetzan, flying backwards just
like rewinding a movie. After hovering at the Gadgetzan FP for about a
minute the trip continued like normal to Theramore. Very strange, too bad I
didn't get a video of it
Devast8or