Well, in order for your Treo 650 to work via USB (or anything, for that matter), it will *always* have to be recognized by your Linux system.
When the device shows up in the output from "lsusb", that's great, and exactly what you want. However, when it doesn't show up, I would do the following;
1) Make sure you have a good USB cable (I had that exact phone and the cable that came with it was a total flake)
2) Check the output from the "dmesg" command, see if a module (aka "Driver") crashed when it saw the device and started to initialize.
There could also be another problem; which port are you (always) plugging the device in? I've seen a few laptops & desktops that had the inside "tab" if their most-used USB port snap right off.
P.S: Apologies for the *really* late reply! Happy 1 year anniversary!