I have more experience to report.
First, to review.....
I have an mbox 3 that works ok on two computers. One uses Windows 7, the other XP. The mbox 3 does not work on a third computer, a Compaq laptop running XP. All I get is the sequential 'chase light show.'
I have tried reinstalling the OS, Pro Tools, the mbox driver, & the USB driver to no avail.
The mbox does, however work fine on the problem computer when I use a port replicator.
Now, here is the new part.....
I went to Best Buy and purchased a powered USB hub.
http://www.bestbuy.com/site/Dynex%26...hub&cp=1&lp=12
When I connected the mbox 3 to the powered hub, it settled down and worked ok 'stand alone' even before I started the computer. I started the computer and the mbox then started flashing the blue power tly. I reinstalled Pro Tools and now it works fine.
Note that I am using the same USB port on the computer, the same drivers, etc. Everything is the same except I added the powered hub. I consider this to be fairly strong evidence that the USB power in the Compaq laptop is the culprit.
Please note that I am NOT saying that USB power is always the cause of the failures & that the powered hub will fix all instances of 'light show' or 'hardware not found.' It is just one of the fixes.
I will continue to make some more measurements as time allows to further confirm this. If anyone else is having an mbox 3 problem, please post the details here and I will try to help.
IHTH