Can't move my spacecraft at all

[Tbone]

I've run in to this problem on a couple of spacecraft: they won't move. Obviously, I checked for fuel and electricity but those are plentiful. I'm using Mechjeb to control them but the problem seems to happen when I switch to the spacecraft. One thing I noticed on a small probe with this problem is the body is flexing as I attempt to turn it but it doesn't turn.

[Padishar]

I've seen this a few times but it's always been fixed by either going into map mode and back or switching vessels and back.

Pad.

[Bobe]

I've found that after undocking a ship, MechJeb sometimes freaks out and decides to control it from everywhere, resulting in the ship trying to move but remaining stationary. Once I manually choose where to control from it "unlocks" and moves properly.

[Max Grant]

I have had rocket stacks snap on me before, and that gives the same effect. Make sure you didn't break in half or something. They can do that in flight and appear to keep going correctly but when you go to stage nothing else happens.

[TechnicalK3rbal]

Are you still in the time warp? the game doesn't simulate physics if you are, meaning you cant move.