KSP version 1.0.5, Windows 8.1 64-bit.
This is an absolutely fresh clean install, no mods. I double-click KSP.exe, and then Windows freezes. i can move my mouse, but cannot click on anything/close windows or anything. The only thing I can do is ctrl-alt-del and end the KSP task. If I try double-clicking the launcher, I get a blank window that pops up for a moment, then freezes exactly as before. I have tried running both as administrator with no luck. Originally, this one was on a manual install. I deleted everything, and downloaded the installer version and ran that. Same results.
