FYI: I figured it out with some help from another forum.

OTB, the Blackjack will install certificates that are in DER encoded. Initially I was attempting to import a certificate that was in Base-64 encoded. The BlackJack refused to open the Base-64 certificate (stating 'Cannot access certificate'). It turns out that both DER and Base-64 encoded certificates share the same 3-digit file name extension: .CER which can make things confusing.

I had to go into the Windows MMC and add the Certificates Snap-In on my computer to access the 3rd party certificate. I selected the certificate and exported it in DER encoded binary X.509 (.CER) format.

Copied the exported file to the Blackjack (into \My Documents) and opened it from the device. The blackjack recognized this .CER file and prompted me to add it to the Root CA on the device.

Anyhow, hope that helps someone else out there who might have had the same problem as me.