ZES and Windows 7

Now, I know this isn't supported in any way, shape or form. But there
really isn't any where else for me to take this so...

I have thrown the ZES client on some Win7 test machines as a part of my
rounds of testing and have run into problems. The big one is on the
client, when trying to Check-in with the server, get's a ...

"The underlying connection was closed: Could not establish trust
relationship for the SSL/TLS secure channel"

error. OK, Cert error probably eh? No problem, import the cert into IE(8
of course). Browser no longer barks about an invalid cert. Reboot for
good measure, log on to the machine again and... same thing.

Any ideas? Thanks for your time.