I have little doubt that I inadvertently clicked something or hit some unknown hotkey that caused this, but all at once I can't copy anything from one location to another. No matter what I do, DOPUS creates a shortcut instead of copy the files and folders.
Via drag & drop? Tap your Ctrl and Alt keys while the window is active. Windows may think they are being held down.
If that doesn't help, did you change your drag & drop settings recently?
Or are you copying via something else? Most other modes of copying things (e.g. the Copy Files button on the default toolbar) could not create shortcuts implicitly.