Can we reopen this question?
One of our users here has the exact same issue.
4.13, Windows7 → UEditor displays the same error message.
The DLL is present where you mentioned and its integrity cannot be questioned (it is used by all our users via source control).
I would surmise that there is something integral to Windows7 which causes this effect to trigger.
I tried all the aforementioned suggestions except reinstalling since we deploy our own built binaries via source control and only one of our users has this issue.
If any debugging/tracing is needed, I will gladly trace any code you want using the debugger to figure this out. At the moment, this makes it nearly impossible for this user to test his changes in game.