I think you have to tell more in detail. I have no idea this way.
It's working fine here with usb 2. I'm not an expert, but I could try to help?!
Is your Bios able to manage usb, is it usb 2 or 3, is all software present (see in the repo (if you like, I give you a list of what is here present as far as I can see)). Is the usb filesystem right, so formatted with some filesystem (fat, ext3, ext4 etc?) That kind of info, Keith.
What happens when you try to mount the key? (mount /dev/your usb-key/ in the terminal). Etc. Some people do have problems with usb 3 and Lxde, it appeares on the web.
Have you tried to see the thing in a partition-editor (partition manager, parted, gpated, kde partition manager, palimpsest (very good), etc.)?
Naturally doing things I like it. Great info..........