This is the same problem we had with the Boeing 757, until Mike Gibbs tweaked the aircraft config file. I'm assuming you are flying FSX. I have flown the Dash-8 a couple of time in FSX and did not experience this problem, however, the B-757 did not do this at all airports either. I wasn't experiencing any problems with the 757 until I took it to the airport where Mike was experiencing the problem. This kind of thing would show up periodically in FS9 as well, and it had more to do with the scenery than the aircraft. There was one taxiway at Pittsburg (KPIT) where the aircraft would sink to its belly into the concrete (fresh concrete???) Have you tried different airports?
EDIT: One thing you can do to avoid the crash is to taxi at a slower speed over that portion of the taxiway.
Bob S.
Senior Command Captain
E.V.P. Scenery