i can't open email with digital signature!

[Warner]

Hi sir,

I cannot open the email with digital signature, and I got "Your digital ID
name cannot be found by the underlying security system" error
And the methods I have tried are follow:

1. Check the IE setting --does not work

2. Create a new profile--does not work

3. I have updated the 128-Bit Encryption Provider for Outlook 2000
SR-1.--does not work

4. Outlook safe mode--does not work

5. Try to open in OE--does not work, I can open but the body is empty.

I am using Outlook 2000, Windows XP, Exchange account ( I am on the client
side)

Please give me some advise about this issue.

Thanks a lot

Warner