Self Cert Signature now has problem?

Hi all,

I'm running Excel 2000, SP3, Win2K SP4.

I had created a self-signed digital certificate for myself so I wouldn't
have to deal with macro warnings for my own project. All was fine and good.
Then, one day, I made a change to the code, which I've done since signing
the project, without any previous problems, but this time, when I made my
change, and went to save the code, I got this message from Microsoft Excel:

"There was a problem with the digital certificate. The VBA Project could
not be signed. The signature will be discarded."

And now I get the macro warnings when I open the file.

I tried creating a new digital certificate, and signing the project with
that, but I get the same error message.

I don't think I've upgraded anything since last time that I saved changes to
the VBA project.

What can I do to fix this?