I've seen this where the "network location" is mentioned and you are using a DLL locally (i.e. not remotely) - but it was copied from a remote location (e.g. internet file share site).
The trick in this case was I suspected the DLL was blocked due to the streams concept, but the explorer UI properties dialog did not show the "unblock" button.
To work around this, I used the sysinternals tool "streams" (found here: Streams download) like so:
streams <your dll> -> view stream
streams -d <your dll> -> delete the stream data on a file
There's also a recurse option with -r if you want to target a group of files.
I hope this helps someone else - it was tricky because the UI didn't show it was blocked, but it clearly was (perhaps due to some other security measure here).
This solution also means you don't need to adjust the loadFromRemoteSources flag, as that is quite a broad stroke.