I have a problem when using PMDG 737-600/700.

When I load the plane, I do my start up and noticed that the fire bell would not work and about 10min into the startup, the FMC screen flickered and frames dropped to no more than 5fps It does this in all of the windows ie. overhead, throttle, FMC.

When you switch to the outside view the frames are normal.  Also when you use the hat switch to look sideways or at an angle, the frames are normal.

It has happened twice now so PLEASE help I would be lost without this plane

Thanks......Chris