I have a PC at home and one at work. When there are certain USB devices, most notably USB flash drives, the systems will hang until these devices are removed. There are, I believe, several servers that have the same issue with a USB hard drive enclosure. Once the devices are removed the system boots fine, once the OS is loaded the devices work like charm.
I thought it was limited to storage devices but this doesn't seem to be the case. I had the same problem with an old Philips webcam.
Any insite as to what is happening here would be much appreciated.