Same problem with my Intensity Pro 4K and a dual Xeon-based editing system. I get the unsigned driver error many times during install and when it reboots, the driver isn't loaded because it's not digitally signed.
I'm on my sixth install attempt. I've tried the hacks for disabling driver signing, and I've even tried a tool to patch the driver to supposedly make it digitally signed. Nothing works.
The irony is this is my second Intensity Pro card. The first one installed with difficulty on a 10 year old Core2 Quad but after 3 attempts, it finally worked. But on the new SuperMicro dual Xeon, it just won't install no matter what.
Back to Amazon for a refund.