very strange behavior B1900D

Hi,I'm using the B1900D with a VA provided repaint.When I start the engines, my frame rates drop by almost 3/4 from about 25 normal to about 6. I turn off the engines and the frame rates go back up. It's repeatable but I don't remember having this problem with other repaints.Sound is set to medium quality. Lowering that did nothing.I am going to try the default paint, different airports, etc..Any ideas on what would cause such strange behavior?Jeff