Crisis averted.
There's some kind of ridiculous bug with the way ME2 and 3 know if your save games are 'corrupted' or not, that's a generic error that pops up when your save games are 'not yours'. How do you make them 'not yours'? Easy, just do what I did and upgrade my 360's HDD and copy all of my old content from the old HDD to the new one. The solution, then, is to simply copy my ME2 save file from the HDD to a USB memory stick, and then copy it back to the HDD. That's it, doing this makes the save game 'yours' and you can import it into ME3!!
I hope nobody else ran into this error and threw their hands up and went on to creating a new Shepard which isn't theirs. My Shepard is from ME1, I would have been really pissed if my save games really were corrupt.