How to change Security Policy for a non-app program (ssh)?
Check .ssh/id_rsa and make sure you still have these lines on top and bottom:

-----BEGIN RSA PRIVATE KEY-----
-----END RSA PRIVATE KEY-----


They are crucial to the functionality of the SSH PubKeyAuth setup. Looking at the output from your debug, it appears that SSH is complaining about not knowing what type of key it is, which is defined by the first line. Likewise, after considering this, I removed the first line from my own private key, and SSH suddenly started bugging me to enter my passphrase for the key.

If this solution doesn't work, I'm afraid your only option will most likely be to re-generate your key pair.