I had this problem with one of the Boeings (can't remember which one), but then I started releasing the parking brake before pushback, and waited until I'd stopped at the end of it before re-applying, and everything was OK.
Then I discovered Rob Barendregt's pushback/taxi speed gauge, and I use that now. (Search for 'Barendregt' on Avsim, and you'll get all of his gauges.
