All,
I believe after some testing I have managed to resolve the broken Pipers issue. I tried many things and nothing seemed to work and then it struck me that I hadn't switched to a compeletely different plane. So, I switched to the default Cessna (the original 172) and started a flight. I then put myself back in the Piper Arrow IV and all was, once again, right with the world. I just completed a 2hr flight to El Paso and it was a great flight!
I'd like to thank you all for your help and I hope the above notes serve to help another.
Good day.