I have not yet had an opportunity to check for myself or not and now its really bothering me... I had a saved game in single player mode about halfway through act 3... I had a few friends over the other night and a buddy of mine started playing single player mode and went to start a new campaign instead of continue... did I lose my progress when the game he was playing saved??

you will hav eto load a previous chapeter, like chapter 3 section 4. but any check point you hit in thaat part is gone. no big deal really. the check points are pretty often actually, still kinda sucks though

Thats not that big of a deal, I was just worried I lost all of my progress... thanks!!

i think its a bit strange how when you start it up, it defaults to 'start a new game', not 'continue'. doesn't make any sense to me