HandSpring Visor Deluxe HotSync problems, especially with Palm Desktop 2.5

Brian Shaw reports a problems with using Palm Desktop 2.5 on the new Handspring Visor Deluxe PDA:

Just received my Handspring Visor Deluxe. After installing the Palm Desktop (version 2.1) and associated software from Handspring's CD, I was able to successfully synch the Visor to my Mac Beige G3 (w/ Entrega 2-port USB card and OS 9). However, although the USB port was selected in HotSync Manager, that application opened my serial port, so I could not then use my modem until I manually turned HotSync off. So I uninstalled the Handspring software and installed Palm Desktop 2.5 package. At this point, HotSync no longer worked at all.

Although not mentioned in the documentation nor on Handspring's web site, a technical support rep confirmed by telephone that the Visor is currently incompatible with Palm Desktop 2.5. They are researching a solution.

Update: As Tim Cox reminds us, there may also be a more general OS 9 issue at work here. Apple TIL article #60654 states: "USB Adapter Card Support 1.2 is not compatible with Mac OS 9."