The first fumble, yes, I agree, it was Losman's fault. He held the ball too long (he did that often today; makes me wonder a bit if this bargain basement WR corp was getting open).
On that 2nd fumble, that was one of the more pathetic attempts at a blitz pickup I've seen in a while. That one is as much on McGahee as Losman. Granted, I think McGahee tried to pick him up, but failed miserably. I don't think its unreasonable for Losman to have expected McGahee to have been more effective on the play.