Mods seemingly broke a pre-mod gamesave, but how?

[vger]

So I tried installing some graphic mods today. One of them wasn't cooperating so I removed it. Then I suddenly noticed my old career game was gone. Trying to load a quicksave showed all of my quicksaves were gone as well. Verified the game cache via steam and two items were shown to be borked and it redownloaded them. Still no change.

I scanned my HD for the savegames and found ONE of them and restored it. It told me the file was incompatible with the current version.

I deleted the whole ksp folder and redownloaded it. Then I dropped the sfs file back in and tried to load it. Still incompatible.

What is very weird about this, is this savegame file is from yesterday, BEFORE I installed any mods. I made no attempt to access this file while the mods were installed, but somehow it is still incompatible.