Windows Cryptographic Service Provider Error 2148073499

I've got Adobe Acrobat 9 and when I try to digitally sign a PDF document, I can get all the way to where I see what the signature will look like, but when I click on Sign, I get an error window with the following error:

The Windows Cryptographic Service Provider reported an error:

Provider type does not match registered value.

Error Code: 2148073499

How do I fix this?