SSH private key to Ubuntu works from command line but not using Remmina

I have been trying to figure out why I can't get SSH working using Remmina SSH client. In an Ubuntu 12.10 environment, I can connect with my server from the command line using openssh server, like this:

ssh -i privatekey.pem username@hostIP

Everything is good using this way.

But now I want to connect a remote desktop session to the same server, but I need to connect through an SSH tunnel. Anyway i have xrdp running on the server and I will connect using RDP through an SSH tunnel, I am using Remmina Remote Desktop program to do this. But first i just wanted to use Remmina SSH to make sure that was working. And it doesn't work! Each time I try to connect I get this error:

SSH public key authentication failed: Public key file doesn't exist

The settings in Remmina for SSH are very simple:

host
username
indentity file (privatekey.pem)

Does anyone know why SSH works in the command line but fails to work through Remmina? Is it a bug in Remmina? Or am I missing something?

Thanks!