Certutil -repairstore Access Denied - Windows Server 2008 R2

I am trying to recover a lost private key for a certificate on a 2008 R2 box (web server cert, issued by Thawte) and when I run:

>certutil -repairstore my "cert serial #"

I get:

>No key provider information
>Cannot find the certificate and private key for decryption.
>CertUtil: -repairstore command FAILED: 0x80090010 (-2146893808)
>CertUtil: Access denied.

I am domain admin, and running the command in an Administrator:Command Prompt.  For some reason I vaguely recall something about permissions to the keystore needing to be modified, but I have slept since then so I may be way off base.  My searching is failing me this morning, so hopefully this is an easy fix (short of revoke/reissue the cert) that someone else has encountered.

Thanks in advance.