Man, am I glad to have found this thread and its predecessor. My Yager did the same thing two weeks ago. No indication of any problems, then it wouldn't start, then it wouldn't stop trying even with the key out or the stand down. My dealer here in Austin was flummoxed by the symptoms and even thought someone had reversed two wires connected to the starter. Kymco told them my warranty couldn't cover the problem.
I copied these threads to the dealer who passed them on to Kymco and, voila, they'll be replacing the starter and the battery, as well. Thanks to Brian at TJ's Cycle for his persistence. And thanks, Forest Grump, for this thread describing the problem and solution!