After several fantastic flights with a PZ Super Dec., today it decided it had enough of flying. I hand launched as usual, full throttle, slightly nose up, and it went nowhere. The plane started to drop, and I added a bit of up elevator- nothing, it just dropped out of the sky from about 10 ft. I flared it a bit and was able to land "rough". After a brief inspection and control test, I tried it again. This time it climbed to about 50 ft, and I started a left turn around the pattern. Again, it lost altitude and This time it nosed in from about 5ft. The plane is undamaged, and the control surfaces are all responding as they should. I flew two batteries through it yesterday and all was well. What could have caused this? Any suggestions? I have a new prop on the way: a 10x4.7 as recommended in the RCU review. I'm wondering if I should even try it?? -Paul