I have a habit of making mutiple save slots and I also use quicksave and autosave most of the time so I usually have around 6 savegames in the game menu. Every time before I quit a game I save it under one of existing slots, overwriting the previous one. It all seems fine, I exit the game and sometimes the game crashes, but most of the time not. But then I go back into the game and my latest save is missing! As I already said I keep multiple saves and autosaves so it never happened that I would have to replay some part but it's still annoying and strange. That doesn't happen often, I haven't had this issue for months now but today it occured again.
I have Windows 7 64 but I can post other specs if necessary.