After running a few more tests I realized that I was in fact signing the driver correctly with the cross-certificate because it now loads on Windows 8 x64 and Windows 10 (technical preview) x64. I do however have a major problem since Windows 7 x64 will not load my signed drivers. I ordered the SHA-1 specifically to sign drivers and avoid this kind of mess. How can I verify that I do in fact have a SHA-1 cert? I've read on here that SHA-2 has issues with Windows 7 and vista driver signing, perhaps I was given a SHA-2 cert?