From a command line (in FC3/FC4), type the command dmesg. That will show you a list of recent USB events.
Also from a command line, you can type su and then enter your root password. Then, type:
[rootXXXXXX] "cat /var/log/messages" (without quotes)
to see a list of events that are not only USB. (Don't forget to eventually type "exit" to get back to the user level and not have "root" at the left.)
These two commands can help you in fixing all kinds of USB problems you might encounter.
I started playing with my webcam in order to help Nay_Nay and discovered that it doesn't work after upgrading to FC4. It's an almost no-name camera called "Hawk" and the box for it is long gone. I got it working in FC3 by seeing:
Chipset: xxxxxx, etc.
and downloading the right software.
Does anybody know the command that lets you hotplug a USB device and see all these details?
This might be useful for Nay_Nay--and me, too.