IE Certificate Errors

I'm running Windows 7 64bit. I regularly access a work website that has a self-signed certificate. I got tired of the warning message that always pops up regarding the untrusted certificate, so I installed the certificate. When I used to run XP, that solved the issue. However, for Windows 7 64-bit, that did not fix the problem.

I've also tried installing the certificate into the "Trusted Root Certificate Authorities" store for both my user account and for the computer. That didn't fix it either. Finally, I tried changing the security zone for the site to be in the Trusted Sites list. That also didn't fix the problem.

I find it very irritating that a website that has a "trusted" certificate is giving me a warning message about an untrusted certificate. I wonder if this is related to the Windows 7 64bit driver signing nazi-ism (i.e., you can't load device drivers signed with non-Microsoft certificates, even if you install the certificate). Just for grins, I tried disabling driver signing enforcement, but that didn't change anything either.

Does anyone have any ideas?