Ubuntu update manager fails. help!!!!

[Kevin O'Gorman]

When I try the update manager, it tells me I have 102 packages to
upgrade, and then presents a popup window that says
    Failed to fetch
http://us.archive.ubuntu.com/ubuntu/pool/main/libu/libusb/libusb-0.1-4_0.1.12-14ubuntu0.1_i386.deb
404  Not Found [IP: 91.189.88.45 80]

And it goes no farther.

Something is borked in my configuration, I guess, but I'm have no idea
where to look for it.

Help!!!

-- 
Kevin O'Gorman, PhD