If you are on the Mac platform, but are using the Parallels virtual machine (VM) to run Windows so you can sync your Palm (or similar) device with, say, Outlook, this might be useful to you.
I discovered today that the reason Windows was not seeing my Palm when I plugged it into the sync cable, is because I didn't have the Parallels "Tools" program installed properly. Not sure what happened to it but maybe it got corrupted or something. In any case, reinstalling it fixed the problem of Parallels not picking up the Palm when I had it plugged in (which was really why Windows wasn't seeing it either).
Tools is a program that sits between Windows/Parallels and the Mac operating system and lets the two operating systems "talk" to one another. It allows you to do all sorts of things like share folders between Mac and Windows, mesh the two operating systems together (so the windows appear to be operating as one cohesive OS--called Coherence--it's pretty neat), and so on.
I had been cleaning the connections on the Palm and assuming there was something physically wrong with it or the cables. Turns out it was just Tools needed to be reinstalled.
Once I reinstalled them and restarted Windows (important!), all was well again.