I had the stall problem with a Dreamwings Fokker 50 last night, as I was flying for Luxair. I had to abort the flight twice and reset the FS, but each time the aircraft was passing 2000 feet the airspeed would drop rapidly and the aircraft would stall.
Today I repeated the flight under the same conditions with a different Fokker 50, and there was no problem at all. I came to the conclusion that the Dreamwings one was faulty and deleted it from my collection.
So sometimes this problem may be just down to a faulty aircraft and not your flying skills.