When I was contemplating buying my 848, I spoke with a couple of 848 owners who happened to be at the dealers. Both said they'd had problems with their gearboxes and had work done under warranty. This was the pre Evo 848 they were talking about. I know that doesn't help with diagnosing the problem on your bike, but it could well need a dealer to resolve.
Is it trying to click up into neutral when at a standstill??? If so, the clutch needs bleeding. Also, if you have the clutch lever quite close to the bar, try taking it out a bit on the span adjuster.
