This one took me quite a while because it isn’t documented very well…

api-ms-win-core-winrt-l1-1-0.dll is a part of Microsoft.NET, but I can’t figure out which one because it appears to be an optional driver. Found a copy in Virtual Radar Server.

copied it into the system32 and syswow64 directories and the issue is solved.. Adobe Acrobat updates was not the cause, but the only indication pointed to FireFox.. might be the browser plugin caused it, but I can’t verify it currently..