1) I haven't been able to synch with my IIIxe since I installed OS X 10.1 at all!! And to make matters worse, Palm hasn't released an updated version of Palm Desktop since 4.0 on 03/25/2002, which is just crappy for us Mac Palm users!
2) I would advise against plugging it into your keyboard. I've heard sometimes there are problems with the communication being interrupted by keystrokes. Mind you this is highly unlikely, but worth a shot anyway. Try plugging it into a hub or any free USB port on your computer (even if you have to disconnect your printer or something temporarily, just to see).