is that judging from the list of fixes they made, none of them really pertain to single player, with possibly the exception of the memory leaks between level loads. Which makes you wonder what exactly it IS that's breaking your previous save games?
I'm just suspecting lazy coding.
Then again, this game is 5+ months old, is anyone still playing the single player version? I played through it twice, and that was pretty much it, I have to admit (although those two times were a lot of fun).