Some textures are not loading

[Tubusus]

This is an older bug I've had for several months (so nothing version specific, but in 0.25 it got somehow worse), but until now it wasn't such a problem and I have never seen this anywhere else. Besides, recently I've been using a lot of mods and I figured a workaround, so it wasn't (and isn't) anything urgent...

This bug doesn't depend on version (tried both 32- and 64-bit versions)

Problem: Textures in .png (and possibly other) formats aren't loading.

Screenshots:

http://imgur.com/a/AWbou#0

- Also includes big companies flags (which i forgot to take screenshot of), some part textures (now I can think only of External Command Seat) and textures in some mods (when modded).

It looks like KSP can load only .mbm and .tga textures.

Converting textures to the .tga format works as a workaround (I used GIMP 2 to open them and export as .tga file of the same name).

KSP.log:

http://m.uploadedit.com/b041/1412954497293.txt

Looking at the log, it seems it can't load some sounds too. I never realized that in game, but missing sounds aren't as obvious as missing textures...

System Info:

http://m.uploadedit.com/b041/1412955486121.txt

As this bug is present in all my KSP installations (and I found a similar glitch with black/missing textures in Skyrim yesterday), I'm afraid it could be more fault of a system rather than KSP's, although I have no idea what could be the cause...