Setting up my test lab I ran into a problem when trying to complete my certificate request.

I logged into OWA from my machine and pointed to a folder that had full permissions. Upon clicking okay the following error popped up:

Aetech Cert Error

I then logged into the server and followed the same process. The exact same error occurred.
I then re-downloaded the file from DigiCert and tried it again, this time it worked. Seems like a bad download.

Hope it helps.