Now for an example.
Ihad the same problem. Corrupted Raw files on a G5 and on a IMac Intel on a french version of LR and on the english version. I also had a problem with Tiff files. That's why I don't think it comes from the xmp. The corrupted Tiff files could'nt be opened anymore in Psd. I opened them in GraphicConverter and did a save as.
I also had a problem with Raw files on a IMac Intel on which Lightroom was'nt installed. Only Camera Raw plugin 3.7 was installed. May be the problem comes from there?
(please excuse my poor english-I am french)