I've been running KSP 64bit on well over 7gigs of ram for quite some time. It's an experimental install i'm trying to get stable (good effin luck!!). One thing i did notice is that whenever anything is changed about the gamedata folder, it will break all previous saves. Loading them will consistently cresh the game on clicking a part. Reverting the gamedata folder to the previous state will fix it... mostly. The new B9 aerospace 5 won't work PERIOD, not eve on a clean install, ditto for active texture management. Though the latter did work on a clean install, just not with any number of other mods. Parts catalog crashed the game on VAB/SPH load consistently. There are a few other mods I have tested that refuse all cooperation, unfortunately I can't quite recall as this has been an ongoing process for... well forever really, and progress is slower than zombie snails. I WAS running fine with: - Blizzy's toolbar - B9 RC4 (with updated plugins) - Blackhearts procedural fairing textures - chatterer - Connected living spaces - crossfeedenabler - custom biomes - DR - Distant Objects - EVE - FAR - Rastapropmonitor - interstellar light - Engineering redux - nav instruments - hyperedit - BA v5 - Cool rockets - KM Space Shuttle Engines - KSPRC (without the sound mods) - Mechjeb 2 - Cargo Bays by Tal - Hot Rockets - Docking port alignment - Final frontier - ORS - Procedural dynamics - Procedural fairings - Procedural parts - Remote tech 2 - ScanSat (plus RPM) - Ship manifest - SPO - SMokescreen - Surface lights - Texturereplacer - TACLS - Kerbal alarm - Tweakscale - MKS/OKS - Karbonite - DERP lifeboat mod - Us core - US tac - Vesselviewer for RPM - Module manager 2.3.5 This was working just fine, hours of playtime into the savegame. Then i added Realfuels with stockalike engine configs to it, and it proceeded to crash every time i click any part. I removed realfuels and the stockenigne configs but the game still continues to crash each time i click a part. So it's back to square one... One thing is for sure, 64bit KSP is a major PITA, once it starts crashing, good luck getting it back to do anything BUT crash. That being said, it does seem to persistently crash with certain mods installed. B9 is a particularity hard mod to install, as is KM's shuttle engines. I had to delete the fueltanks from the KMSSE mod to get it to work, and the B9 RC4 "sort of" works, as long as you can live with some freaky saber engine behavior and the odd crash on clicking a part. The rest of the mods I've listed are more forgiving. MKS/OKS gave me a few issues at first, but sticking to a clean savegame fixed those.