The problem lies within openssh when key is read, it will validate buffer size with filesize which will differ and produce the following failure:
2014-10-16T10:31:50: ssh[E]: debug1: key_load_file: key file C:\\data\\id_rsa changed size while reading
Only affects Windows as it is the magical \r\n to \n translation that screws things up. Fixed in r29994.
Re-fixed in r29997.
Works well. Tested on Fedora 21 and Windows 8.1.
Created a broken key using notepad and test with 4.3.0 client and verified that it was broken (a password less key presented a password prompt). Loaded the broken key into client build 4695 and it worked as expected.