I haven't heard about a problem with the array arm (solar arrays?), and I'd appreciate more info. In the meantime, I could speculate on general principles that if something happened to change the configuration of the spacecraft, then the "self image" embodied in the onboard guidance software will be wrong, and thruster firings won't produce the expected result. MGS could well end up tumbling as suggested by the Express results. If the error is large enough the software might have expended the last of its fuel in a futile attempt to restore attitude.

I could well be sic transit gloria time for Mars Global Surveyor. She's been a beautiful spacecraft and a thoroughbred explorer, and turned the world (Mars) upside down. We won't forget her.

And raise a glass for Michael Malin, designer of the MOC and until MRO reached orbit, Grand High Panjundrum of high-res Mars imagery. Science depends on its instruments, and Malin's camera opened the floodgates of discovery. Way to go, Doc!