10.4.2 vs. Palm Desktop 4.2.1 via iSync 2.1, FIXED!
Fix: 1. Removed "Palm HotSync" folder from /Library/Application Support, archived on Desktop for safe keeping, trashed original, restarted to disable running apps.
2. Ran iSync 2.1 (88.0), which crashed repeatedly for some reason. Decompressed "Palm HotSync" folder and returned to /Library/Application Support while iSync was still running (the one time it didn't crash).
3. Selected option to "Enable Palm Device", and lo and behold, it suddenly offered to move various conduits prior to installing the iSynch conduit.
4. Ran Conduit Manager from with HotSync Manager, selected the option to allow iSync to manage whatever goodies it can.
5. Did so, and suddenly my Palm device (HandSpring Visor Prism running 3.5.3) showed up on the Synch bar.
6. Pressed Synch button in Prism cradle, and success!
Conclusions: Apple didn't do the greatest job of making Tiger work with Palm Desktop, but it must be some kind of gerflummoxed permissions problem and fairly "manual" at that. Go figure. Hope they fix it for regular users soon, or there will be a great wailing and gnashing of teeth in the PDA crowd....