Exactly what Mark said, I also think the problem might be on the flutter on the previous flight. A flutter can basically loosen all your jet and can damage critical parts without you noticing it. After the flutter you should have stayed on the ground until you figure out what went wrong.

I also think the Viper was going quite fast on the loops, I have stalled mine to the point of full up elevator and no problems. Maybe the CG was not correct...

I also experiensed the problem with the 14mz, almost lost an F-4 which became very unstable durring a flight...

Too much maybe's I guess.... Sorry for your loss...