fsx BT shuts down fs at end of flight

My BT B-25 shuts down fsx whenever I try, within FSX, to end the flight. This happens whether I have been flying for a while or just sitting on the runway reading thru check list etc. Time is not logged and have to re-start the program to fly another plane etc.

HP Pavilion, 8mb, Vista Home Premium SP2, Intel Core 2 Quad CPU Q8200 2.33 GHz, 64 Bit.

Plenty of HD space

GeForce GT520, Total avail graphics memory 4mb+, dedicate video memory 2mb+.

Thanks

cmitch47

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