I just upgraded our Exchange 2010 server to the latest version, service pack 3 roll up 5. Since that upgrade, a few users (out of 40, maybe 5) are getting the security pop up. We have a terminal server running and I was just told (and confirmed) that it is also happening on that system. We run Windows 2008 R2 servers.
The exchange server upgrade is the only thing that has changed.
I've gone through the settings on the Exchange server (EMC) but everything looks fine there. Since it was working fine before the upgrades, I'm really not sure what to look for at this time