I've a suspect that a program I installed (spideroak) didn't completely removed itself on uninstall. How can I check if there are still file system hooks installed?
Probably spideroak wasn't the problem. For some reasons git-cheetah shell extension got enabled on my PC and was interferring with stderr (I've GIT but it's not even in the path... I've a special batch file to add it that I use when working with GIT repos).