Riding with several dozen other riders eastbound on 40th street, just after crossing Park Avenue, a police officer on a scooter nudged me over to the right hand side of the street. After some delay and discussion with three other scooter cops who were standing around he gave me the ticket and explained that it was for "not riding to the right hand side of the street."
I pointed out that I had been riding to the right hand side of the street, or as near as I could get to it on the opposite side of a row of parked cars. A concerned witness observing from the sidewalk also pointed out this fact. The police officer did not reply.
After returning home (having lost the other riders) and reading up on the exact rule cited on the ticket I have realized that even if I had not been riding to the right or left side of the street RCNY 4-12(p)3 does not constitute a valid citation as it does not enjoin cyclists from doing anything at all. Instead, it merely states that they may ride to the right or left of certain one-way streets.

Update: This was dismissed in traffic court, 6/4/07. The cop showed up to the hearing and claimed to have no recollection of the offense and thus it was dismissed.