Basically the old N710c uses direct serial (part of OS3.52) so you either need to flash part of N760c into N710c (to make it OS 4.1) or find the rare Sony fix (that used to cost $50). One poster on 1src used to offer it but his link is down.
Supposedly Sony support offers a way to get Desktop 4.01 driver that you add to make it work. (OMG22UPD). I did get frustrated last night and just might make my N710c into a museum piece.
Th-55 U, T/X, TG-50, Handspring Deluxe (3) and PSP user.