I had the same problem - turned out to be the speed sensor. It is located on the right hand side of the bike, underneath, seating into the gear box and held in with two screws. One is very easy to remove, the other a pain due to the centre stand.
Replacements can be bought from you local shop for about $150 and are easy to fit... Remember to drain the oil first and save the 'O' ring. The new one does not have one in the kit.
The connector is a simple two pin plug, behind the fairing on the right hand side.
All up takes about one hour...