In my quest to find out why my Handspring Visor couldn't log w/ MMCd and what I thought was the correct cables, I stumbled into this page which link I'm posting in the hope that those who are in the process of setting up their datalogging system check this FAQ for valuable info regarding cabling and demystifying why certain cables work for certain pda's and certain cables don't.
Good info for Palm Pilots as well as those with other pda's like me, (Handspring, Sony) who wonder why their logger won't work.
Hope this is useful to all of you. Plus thanks for all those who have tried to help me!

http://automotive.miragecorp.com/Support/OBDIFAQ.html