I’ve just encountered this error message.
This happened right at the very first launch of Syncthing with no pre-existing configuration. The environment is Windows 7 x86 running in a VirtualBox VM.
Have you got any idea what the error is about, and also whether this is something serious or rather something that can be ignored with no repercussions?
Edit: The error re-occurs on each subsequent start of Syncthing. I suspect this may have something to do with Windows 7, as I’ve never seen the error in newer versions of Windows that I normally use on a daily basis. I don’t remember seeing such errors previously in the exact same OS though, e.g. a few months ago. This installation of Windows 7 is almost entirely vanilla with no specialised configuration, especially regarding networking and such.