I have the same problem on my laptop with a 32bit windows 7, no problems on my main PC under Win7-64.
I can play for a bit, but if I explore too much my game eventually won't be able to save. It's really annoying, I actually stopped playing completely on my laptop.
This is the kind of thing that would make me want a refund if the game wasn't in beta, I hope it will be fixed before release. Not being able to save in an RPG is quite a problem.
