Vista - Signed driver on Vista64 not recognized

Hi, I finally have my File System mini-filter driver working great, and tested it a lot on Vista 64-bit using the testsigning boot option. All was fine.

However, when I turn testsigning OFF and try to start the service (the driver), I get the StartService failed with 577 - windows cannot verify the digital signature. Note that the driver in INSTALLED, and the Registry is updated, etc. I just can't start the service (even when running as Admin).

It is signed using a Microsoft cross-certificate, based on the original certificate issued by GlobalSign, as directed in MSDN. You can examine the certificate using the driver's properties, and all looks fine.

I also tried installing the certificate, but that made no difference. This should all be correct, except that it doesn't work!! Any idea what is going on here? Any help would be greatly appreciated! I thought I was all done with this project, but since it doesn't work, I am currently screwed. THANKS!