SSL inspection cause IE to give TLS errors

Our locations are locked down by their FortiGates fairly rigidly (FortiOS 5.0.14). We have one site that has recently been being blocked that is regularly used (www.concursolutions.com). This has always been part of our web filter whitelist. We are finding that It can only be gotten through the firewall when SSL inspection is disabled. I have tried adding policies before the primary internet traffic policy point to the site as well as its CRL location, and it DNS records IP address for both default and www (point to Microsoft). None of this works. TLS is already all checked by default at all locations in IE (no other browser can be installed, nor do they have permission to do so). Since it is below 5.2, there is no way to add SSL inspection exemptions. Any thoughts on how to achieve this would be greatly appreciated.