Thanks. You saved me hours of time.
I find that with the older ibm thinkpads you have to set usb to "enabled" in the config area of the bios.
Then for additional insurance I might actually set the CD rom (or USB) I'm trying to boot from as 1st in boot order.
Finally I try to engage the manual boot menu at the splash.
After that I have been known to use my sledgehgammer and forget the whole idea-but that's just me.
...oh -not if it's a customers machine tho.