For others having trouble with this - a temporary workaround is to just select the text and drag it into the application you need.

I am encountering the same problem.

In my case, I cannot copy/paste anything from the "viewer" / "editor" panes in Haroopad Windows. CTRL+C simply has no effect: when pasting, it only remembers what you had copied before hitting copy inside Haroopad.

I just upgraded Windows 8.1 to 10 and can confirm both OS's are affected.