JBK and A1 Flight Planner

Hi... I seem to be having a problem with JBK aircraft in the A1 Flight Program. I start by selecting a JBK DC-6 from the list, go through the compiling and then open FS9 to look at the aircraft. The JBK DC-6 starts down the taxiway normally and gets into position on the runway without a problem. Then it starts out at about 10 -15 MPH but never goes any faster than that down the length of the runway until it finally hits a tree or a building but never taking off. Has anyone else expierenced this problem.

Thanks