Same issue here... I'm at a light and decide I'd like to leave the world behind me...
I get to 6500RPM, grab the clutch, up-shift to 2nd, and it doesn't engage. Now I'm still miles ahead of traffic but with no momentum.
So I pull the clutch in again, by this time I'm decelerating, not accelerating, the bike slams into 2nd and I'm on my way.
Doesn't happen all the time, I would say 3 out of 5 times. Very disappointed when it does.
Any ideas before I go to the shop and they tell me it's not a sport bike and to stop riding it like one.