Using public key authentication on the Windows ThinLinc client you will get an error saying:
"The selected key can't be read or belongs to someone else. Please try again with a different key file."
This happens when the client is started with a public key file already chosen. If you selected a key file the last time you ran the client it will be saved for the next time you start the client.
Tested this and it works for Windows 10.
Verified that the problem existed with 4.10.1, but was actually only able to reproduce it when running the 64-bit client on Windows. We tried multiple times with the x86 client and it never showed the problem.
The fix looks good, however. Verified that a pre-selected file always worked fine using build 6255.