This does sound a bit like a problem that i am currently having...
I have been told that it may well be the hall sender unit. when i drive down the road it will be fine, then all of a sudden the revs drop to zero, all power ios cut and then it just rolls to a hault by stalling, i try and restart and its having non of it untill i leave it for a while.
but i have resulted to giving the plug a wiggle and moving the wires and then it starts up a treat!

(obviously this is pemporary and it does need fixing!!)
x x x