IE blocking website from displaying content

I'm getting the annoying messages from Internet Explorer (7,8,9,and 10),
'Internet Explorer blocked this website from displaying content with security certificate errors'.

The PC are Windows 7 and the Servers are Windows 2003, 2008, 2008R2, 2012.

I have search the web for many hours trying various suggestions with no success.

Before someone suggests that I check the time on my computer, it has been checked and rechecked. This does not appear to be the issue.

The only PCs/Servers that experience this problem are behind my lab firewall. Normally they are in an Active Directory domain isolated behind this firewall but they don't have to be. My DCs (PDC Emulator) sync time with 'time.windows.com' and I'm seeing no time related issues.

Outside of my firewall is our corporate network. I don't see the problem on any system there. At home behind my firewall I don't see the problem. It seems to be isolated to my lab and the lab Cisco PIX firewall seems to be the common denominator (I think).

Are there certain ports that must be open to let this work?
I'm looking for fresh ideas to solve this annoying problem.

BTW. Firefox works fine......

Thanks in advance,
Ken