MySQL SSL error, only when connecting from windows/osX

This looks like a cipher related problem. Try adding the option on both server and client: --ssl-cipher=AES128-SHA. You can use any other suite present both sides in the output of openssl ciphers HIGH.

It's also possible that the MySQL client config file includes ssl-verify-server-cert option, if so remove it or (safer) use a domain name from server's certificate CN.

If it still fails you can:

1. Sniff your connection with tcpdump or Wireshark, look at TLS handshake.
2. Workaround the problem with stunnel or VPN.