Dan, the exact same thing happened to me a couple of weeks ago, i was doing 60mph without even starting the engine :devious
after riding it appeared to function properly again, a day later, 0mph, absolutely nothing :dunno after much investigation i settled on it being the speedo sensor being faulty... a trip to ebay, £37 and 3 days later, i got my new one, absolute :rant to run the wire along the correct path when fitting but once finally done its been fine since
they cant be that fragile because i actually melted the thing almost 2 years before it died, plus i have never exactly been kind to it when taking the back wheel off etc... imho the true culprit was roadsalt/crap getting down the wire, i had the swingarm replaced not very long ago and discovered the protective sheath had been cut right near where the swingarm meets the frame and taped up with electrical tape, which had not sealed the wire... thus water and crud worked its way down to the poorly sealed speed sensor head and ultimately killed it, was interesting to find a much better sealed unit on the new one i got
if you want to double check its the sensor at fault (the other choice is the ridiculously expensive dash unit..) there are some basic tests you can do measuring the voltages at the wire connector of the speed sensor which were fairly easy
Good luck fixing it :biggrin
