Copying into theX11 PRIMARY selection (mouse copy/paste) would not work due to a confusion between content type and clipboard type. Short patch for src/scrap_x11.c from svn below. NB: Not sure if this is the proper forum for submitting a patch but the pygame.org mailing list subscription page is offline.
768c768 < if (cliptype == XA_PRIMARY) --- > if (clip == XA_PRIMARY) 774c774 < timestamp = (cliptype == XA_PRIMARY) ? _selectiontime : _cliptime; --- > timestamp = (clip == XA_PRIMARY) ? _selectiontime : _cliptime;