Hi, good nick :-)
Well, ssh keys in windows systems are actually hell on earth, I tell you.
Assuming you exported rightly all the ssh-keys generated following the manual, it's very likely the process went wrong when copying the ssh key to the server, cause the linux keys are working properly, right?
If so, you might want to copy the windows's key to a notepad and make sure there're no blank spaces and put all of it in the same line. Copy it and paste it in the linux file.
Make sure there's no white line at the end of the file, if there is, it will fail.