Kerbal Space Program

I can't recall when this first occurred, however it has been happening on my install for a while. I am running Windows 8.1 and playing the game in x32. I bought the game from steam, and am running it through the steam program. I have validated the 'integrity of game cache' several times and it has not resolved itself.
Anyway, to the bug now. Most parts have duplicated themselves in the part catalogue, some duplicates having different values to the original. On the occasion (when I had a modded install, this bug happened before I played with mods) when I place a part, it either won't let me let go of it or it breaks the game and won't let me exit the VAB or SPH. The bar where you name the craft disappears and I can't select new parts. I have to force quit the game to exit.
The screenshots below are evidence of this bug in action and it is becoming quite an annoyance to the point of game-breaking. Any help or fix would be appreciated.