Gaming MGS PO Save, and only that, corrupted

[manobon]

So, using PSP 3000, 5.03GEN-C, w/16GB official Sony MS (mark 2) memory stick pro duo...my save files for MGS PO always show up as corrupted, when trying to load. If I go to the Delete save menu in the game, it reads correctly (that is, not as "corrupted data"), with all the details of how many times cleared, etc. The only saves it seems to recognize now are save files made by starting a new game.

All my other games load and read saves correctly, and -obviously- I'd like to avoid unloading then reformatting the memory stick, then loading up all the files again. Anyone know if there's a setting I need to switch or something?

Thanks in advance!