two computers + 1 ipod = confusion

So, heres the deal:

- I have two computers both with ubuntu 8.4 installed. A compaq presario laptop and and a home made tower


- both have the same updates and software installed

- when I plug my ipod (4th gen b&w) in to one (the laptop) it mounts automatically and launches rythymbox on the other (the tower) it does nothing until it eventually disconnects

At this point i'm wondering if it could be hardware related as the software is pretty much identical.

The laptop has an ati chipset for sound and video, an AMD sempron processor and uses an ide harddrive.

The tower is an asus board with an nvidia chipset, a celeron dual core processor and a sata hard drive.

Does anyone have any ideas?

thanks.