Fuel pump continually priming...

During the week I rode my '09 Z1000 to a friend's house. The journey is 9 kms, but about 20 mins, owing to about 20 sets of lights that are timed to get just about every single one red! Anyway, once I arrived, I turned the bike off and took the key out of the ignition. For about the next 20 mins, the fuel pump kept priming over and over again, and then for the next 10 mins or so, there was a continuous high pitched whine. The bike has done 1000 kms (not exactly being ridden hard, I know!
Today I turned it on and let it run for a bit in the garage, and it didn't do it after turning it off then. I have noticed it one other time, but generally I don't hang around the bike after turning it off, so I haven't really noticed it any other times. Any ideas about this,why it may be doing it, should it be a warranty issue?
