scooby, if its the blade 400 with dx6i you are talking about, mine was doing the same thing.

Firstly to rebind, you switch in the TX with the trainer/timer switch held forward and the the receiver already on with the bind plug inserted. NOTE... If you 'accidentally' switch the tx on while the trainer switch is unfortunately being pushed forward by the bag it is sitting on, it will wipe out the bind with your receiver....

Now as for the spinning blades - if you power up the TX/RX when you have the throttle hold on, it will cause this problem. Simply shut down everything and start again with the throttle hold off.

Should fix your problem, it did mine. Oh, and no, you shouldnt have to rebind with a new servo, but once all your trims are reset its not a bad idea to rebind so the failsafes are correct.