OK I will do my best to explain how I got around that SSL Paypal Pro certificate.
First do not read the explanation provide by them..it only make it worse!
Under the SSLCert---Parameter Source insert the following:
cert_key_pem.txt
After downloading the SSL Certificate from Paypal, which I also have an issue I will explain at the end.
After downloading the SSL Certificate to your desktop, I used FTP program call "Total Commander"
http://www.ghisler.com/download.htm
this is the importan part.
I upload the SSL Certificate to www.yourdomain.www/shop meaning your "shop" folder within your public_html where you initially upload all your Viart files.
Now the Parameter source of your SSL Certificate "cert_key_pem.txt" will be seen and will work.
Make sure to add your user name and password properly and when testing live like I do with my own card...to choose your "Please select preferred Payment Gateway" options in order to proceed.
Let me know if that does it for you.
Technizzle my Nizzle, Alfizzle