Internet Security Warning on every Send/recieve

Hi Experts,

We are using self-signed certificate for our server and all the accounts are using POP3/TLS as their account setting. As expected whenever we open Outlook 2007, we get the Internet Security Warning, to which we answer YES and it works perfectly fine.

But from last few days, on one of the laptop the warning comes on every send/receive and everytime we try to send an email. I haven't changed anything on that laptop and all the settings are same on all the other laptops.

Any suggestions?

Thanks in advance..