Talk About Static Cling...

Ground the turntable bearing housing.

Mot I have the same problem with static buildup; it definitly occurs during playback as I too use Zerostat, followed by a blast of canned air for final dustoff before cueing up. Also I use a dab of Last stylus cleaner. I know that my arm is grounded & there's metal-to-metal contact from the arm base to the metal TT deck, which connects to the metal bearing carrier. I'll consider trying the direct grounding approach, but I want to verify (with an ohm-meter) that the bearing is in fact already grounded as I believe that it should be.
Really makes you wonder when you go to remove the previously-neutralized LP & the TT mat then clings directly to it, releasing with mega pops & crackles as the record is lifted away. Surprised that I don't hear static-discharge-distortion pops & crackles during the actual playback.

Make sure your drive belt isn't rubbing against anything.

Providing a drain wire to ground (should probably be the same gound as the cartridge employs, such as the phono preamp ground post) from the platter bearing, as TWL suggests, may be of some help, but I'm guessing the mat might effectively insulate the record regardless. As to the question of why, after thoroughly treating both the disk and the TT prior to playing, there is still a mighty "kling und zap" to behold upon side's end, it's simply the result of the record's spinning motion having caused the static charge build-up to re-form anew when atmospheric conditions are favorable (read: dry). Just don't go experimenting with that stuff you add to the clothes dryer, though...

Zaikes, yes I do not have a turntable mat that could do exactly as you say. Mine is a bare platter that makes contact with the record. If the mat is electrically isolating the record, grounding the bearing housing will not cure the problem. Perhaps a humidifier would be in order in this case.