I ran into the situation recently of attempting to use a USB key to load a Certificate Hash on to a Lenovo T410s. I created the USB key using the USBFILE.exe program. I was able to use the Key to provision an HP 8440p. When I attempted to do the same to provision a Lenovo T410s the machine turned on and just stayed at the Thinkpad opening screen.
After some hunting I found that there might be a possible BIOS issue. I checked and found that the T410s was running version 1.11 ECP:1.08.
I then downloaded Version 1.41 ECP 1.12 and applied it. Lenovo gives you a choice of making a bootable ISO to load the BIOS upgrade. I could not get this to work so I used the upgrade utility I could run in the OS.
After I upgraded the BIOS .......VIOLA USB Key provisioning worked like a champ.
Hope this helps others from spending time trying to troubleshoot.
Below is a link to the actual upgrade. I don't know if the other models are affected but if you see this behavior it might be worth a shot!!!