Github VCS Root - Private Key

Hi,

I been trying for about three hours to create a VCS Root pointing to a Github repository using "Private Key" as the the Authentication method.

But when I hit the "Test Connection" button I get this error back:

"List remote refs failed: com.jcraft.jsch.JSchException: invalid privatekey: C:\Users\Administrator\.ssh\EC2BuildServerPrivateKey.ppk"

The private key definitely exists, and I've even cloned the repository using this same key using GIT extensions.

Surely I'm not the first one to try and use github as a VCS root!?

Can anyone please please help with some suggestions of things to verify?

Maybe I should be using some other "Authentication method" as this one doesn't work?

Thanks!!