Unreal Engine will not start: "The Specified procedure could not be found."


Unreal Engine has worked fine for me for a few months on Windows 8.1.
However, when I started my computer today I got a weird error when I tried to start the launcher:
“The Specified procedure could not be found.”

I get the same error if I run UE4Editor.exe

I am running it on an ASUS N550JV laptop with nvidia 750m and optimus.

Nevermind, I restarted Windows and the launcher is now working.
I have no idea what previously caused the issue though.