korando: yes, there is; you can read the instruction on the download that tells you to close the launcher before applying the patch. Windows won't allow a file that's in use to be overwritten.
UrsusPrimus: the patch downloaded from the launcher is the Paradox one, and it looks for the registry entry that the Paradox installer creates. Apparently D2D's installer creates a different, or no, registry entry and so the Paradox patch will not apply. Patches are the responsibility of the publisher, Paradox, Gamers Gate, Steam and Impulse all have their own versions. What D2D's problem is I don't know, but you'll have to contact them in the first instance to see where they're at in that.