If the exact versions of WordPerfect on different pc's is identical, and the pc's are similar spec, then I would say these are the possibilities:-
(1) A specific Registry setting is different on the two pc's. (Maybe RTF is set to be opened with different programs on the different pc's).
(2) A library file (DLL) is different on the two pc's.
(3) A Microsoft update is loaded on one pc and not the other
(4) A setting in the firewall settings is diffrerent.
RTF Repair Kit - http://www.rtf.repair/