An example of the issue:
I having a problem with a few clients getting my signed emails in Outlook. The error says 'Can't Open this item. An error occurred in the underlying security system'.
Some clients cannot open any message from me, and one of them on two different computers.
I've tried every possible setting in Outlook and I cannot open emails from myself. I even installed my certificate on that system and I still can't read emails I wrote.
Whenever I try to export the certificate via the Outlook 2003 options, it always shows the message 'An error occurred while attempting
to export security information'.



The possible solutions are:

1. This behavior can occur if your digital ID is damaged or corrupted. It can also occur if your digital ID is set up in a single Microsoft Windows 95 or Microsoft Windows 98 profile environment, and multiple user profiles with a domain log on are enabled.

2. The default computer profile has full access to the digital ID, but other profiles for Windows cannot use it. Or if the certificate is not installed on the machine.

3. Check the following Microsoft Knowledge Base article on 'Your digital ID name cannot be found by the underlying security system'

If your issue is not resolved from above points then please submit a ticket to support at http://support.comodo.com and ask for your
certificate to be revoked so that you can apply for a new one.