Thanks @linuxgurugamer for taking a look at this so quickly. I updated to 6.0.1.2 but unfortunately the same issue in some launch contexts. I was running it thru steam with the '-popupwindow' launcher bypass method.
Thanks @Tekaoh for helping figure this out. I can confirm similar results with 6.0.1.2.
"If I run through Steam, now I have an issue. My Steam launch parameter is this: "D:\my-path\KSP_x64.exe" %command% -popupwindow" - Error presents
"If I create a shortcut to KSP_64.exe and point Steam at that instead as described in this post, now I have no issue. "D:\my-path\KSP_x64.exe - Shortcut.lnk" %command% -popupwindow" - Works just fine. I'll probably stick with this method since it works.
If I launch the launcher directly and then open the game thru the launcher, it works just fine.
I agree it seems to be something up with the context in which the game exe is launched.