mbox 2 disconnects

[dishdive]

I run Mbox 2 with Pro Tools LE 7.0 on a Mac ibook G4.
My mbox disconnects from the computer and stops working pretty regularly weither I'm running Pro Tool, Gargage band, or itunes. Sometime I can go to system preferences - Other (click Digidesign Mbox 2) and it will then seek out the mbox and attempt reconnection. Once it's says connected I have to then click on the "internal" clock. At this point it either starts working again or completely locks up and crashes. If it locks up I have to completely shut down and restart the computer. It didn't do this when I first got it so I'm wondering what's wrong.
1. Do I have a bug?
2. Am I missing some update?

any ideas would be much appreciated.

thanks