I finally got a consistant connection from my C3100 to my XP machine, using 2 Kensingston Bluetooth 2.0 EDR USB dongles.
Below is the ONLY procedure that works for these dongles for me.
I've tried other methods, none work. (Cacko Networking applet, and Meanie's Bluetooth GUI applets)
1. Plug in both dongles to USB, (one connects to PC, other connects to Zaurus USB Host cable).
2. su in Zaurus console then, pand --role PANU --service NAP --connect 00:03:C9:BD:2F:0B --nodetach
3. You may need to issue the above command more than once. (First try always gives "Permission denied(13))
4. Issue above command again until connection lasts long enough to access the Windows machine and do next 2 steps.
5. Click, (now green) BT tray icon. Dialog pops up asking for PIN. Type in 1234 and click [OK]
6. Click BT tray icon again. Dialog pops up asking to authorize the connection, click [OK]
Do not place a mark in box which says, "always allow this connection"
(If you place a mark in that box, connection will drop)
I don't know why the Widcomm software doesn't remember my PIN or that I want to automatically authorize this connection.
Since these dongles can actually connect to each other, what is needed to use the more advanced features?
If I use the above mentioned GIU tools, (which never seem to stay connected, or connect at all), I lose the ability to use the "pand" command in console.
In other words, I have to unplug/replug the dongles, and do steps 1-6 again.
