Just tuned in to this thread.
This very thing happened to me on my Surface Pro 3 after applying Surface Pro UEFI update (v3.10.250.0) on September 10, 2014. I could only boot to the UEFI screen.
After two days of frustration and worry, I took it to a Microsoft Store (brick and mortar), and the technical staff there tried various methods to fix it for three hours. They could not boot from USB or from DVD, or even a cable attached to the docking interface.
Finally, they replaced my Surface Pro 3 i7 512 on the spot.
The Microsoft Store technical staff told me that the update 'probably exposed a problem with some circuitry' which only gets exercised and revealed when doing that kind of update. I was not their first. Before leaving the store (September 13), they had me do that same update on the new machine. No problems.
This very thing happened to me on my Surface Pro 3 after applying Surface Pro UEFI update (v3.10.250.0) on September 10, 2014. I could only boot to the UEFI screen.
After two days of frustration and worry, I took it to a Microsoft Store (brick and mortar), and the technical staff there tried various methods to fix it for three hours. They could not boot from USB or from DVD, or even a cable attached to the docking interface.
Finally, they replaced my Surface Pro 3 i7 512 on the spot.
The Microsoft Store technical staff told me that the update 'probably exposed a problem with some circuitry' which only gets exercised and revealed when doing that kind of update. I was not their first. Before leaving the store (September 13), they had me do that same update on the new machine. No problems.