Odd Behaviour

Tonight I took the NGX ut for a flight, after a month of flying only the MD-11....With a few friends also on the NGX we flew to MHTG.....it all started well enough....except when I was taxying for departure I noticed on external view, that the fan blades on either engine were NOT turning!Anyway, climbed to cruise, and I was discussing arrival data when I noticed my aircraft did a very abrupt turn to the left, and continued to perform a barrel roll!!! when it righted itself up again, autopilot was still connected, and it climbed back up to cruise level and resumed the flight....When we performed the RNAV 02 approach, I took manual control by pressing on Autopilot disconnect and Autothrottle disconnect with the mouse...the appropriate lights and warnings came one...I performed the tight turn to miss the hill on final and when I was just on 50ft, my engines went to TOGA!!! I quickly disengaged autopilot and press F1 with the hope of rescuing the situation....just when I was lining up again, it went to TOGA one more time....so this time I gave up, I decided to perform a Go-Around....just as I was cleaning the aircraft, flaps up to 15, etc....and it was on autopilot flying runway heading, it performed yet another hard turn to the left and started doing another barrel roll and my FSX just froze!!One of the guys flying told me he had experienced the misterious barrel roll to the left without warning on a previous flight....is there a fix for this???I am going back to the MD11 in the meantime.... :(