Can't save the game?

[BadWolfSilence]

So I replayed the Half Life 2 series for the billionth time and noticed that I can't save my game. I can quicksave, but I can't actually save the game or save it over any other game but the very last real save ( weird... ) and at first I thought it was just a fluke but it's happening not just in Half Life 2 but in the episodes and even the mods like Black Mesa and Mission Improbable! This is very frustrating and makes it hard to play the game. I looked it up to see if I could find a solution but I can't see anyone else having this problem. Does anyone know how I can solve this or why it's doing this?