Hmm,
Did you try to generate different private key on different machines?
Just want to make sure its not something machine specific.
It appears what happens it cannot validate this private key for some reason and errors you out.
The problem with private key is that if you provide a wrong pass phrase or key it wont be able to tell if key or pass phrase is wrong but will go ahead and try to authenticate.
So I guess I would just double check key and pass phrase or to create a new one if possible and see if it works.
If its not mission critical, you can send me info privately and I can take a look at it if you like.
Hope it helps,
Thanks,
Oleg