Solution: Sometimes you can get this error message while enabling the SSL cert for Exchange 2007. The Exchange commandlet sometime damages the certificate during the installation process. Below are the steps to get fix this issue:

  1. Double-Click on the recently imported certificate.
  2. Go to the Details tab.
  3. Click on the Serial Number field and copy down that number.
  4. Open up the exchange management shell.
  5. Type: certutil -repairstore my “SerialNumber” (where SerialNumber is the number you copied down WITH NO SPACES between the digit pairs)