It sounds like the creat() call is not threadsafe.
It opens a file on disk and while that io is running the other thread spins up and runs into the creat call to open a second file, and boom.
But why would creat not be threadsafe?
Do you have to specify a different, threadsafe version of the c library?
You use to have to do this on unix long ago, but the threadsafe version has become the standard version.

Oh and another complexity; if you do a pull you will find that creat call is gone, I do it a different way now,
but still, that way worked on my side and no idea why it wouldn't work on windows.

Karl Dahlke