Outlook 2007 Unknown Error

I am using COMODO Secure Email v (32 bit version) on a Windows 7 64 bit computer, with Outlook 2007 as my email program. I have certificates for two of my email accounts. I have CSE set at the medium security level.

With one of my e-mail accounts everything works fine. However with the other account I constantly get an error that says, “The messaging interface has returned an unknown error. If the problem persists, restart Outlook.” Restarting Outlook, and even re-booting the computer make no difference, I cannot send email from this account unless I turn the security level to off.

I cannot find any reference to this error message doing a search of the forums. I think both accounts are set up the same. Is there any way to reset CSE settings to default and see what happens? Or any other thoughts.

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Thanks for views and thoughts. I’m giving up, a program should not be so difficult to get working properly with modern computers and systems. I’ll be uninstalling the program in a couple of minutes.