When you try to complete a certificate request in IIS, you receive the following error message:
There was an error while performing this operation.
Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
If you accidentally attempt to apply a public key or certificate response a second time, you will receive this error message as the private key has already been paired and it's permissions have changed. You should verify that the certificate you are installing hasn't already been installed.
You may also want to check the permissions on the following folder:
Administrators should have 'Full Control' permissions to this folder.