There are 2 ways to fix this problem. Before we start off, delete/remove the existing certificate from the store.
If using IIS MMC to import the certificate, then ensure that the “Allow this certificate to be exported” is checked.
If making the private key exportable is not an option, then use the Certificates MMC to import the certificate. Please go through the following KB on how to import a certificate using the MMC: http://support.microsoft.com/kb/232137