From: Juan Lang Ha, right you are. Hm. Well, a wireshark capture of the connection might help, to verify that the web server is in fact attaching the correct certificate to the connection in the IPv6 case.
The URL in question is actually https://testbot.winehq.org/. Browsing there using Firefox from one of the test VMs showed that the server was indeed using the wrong certificate on a IPv6 connection. I've had a stern talk with it and it promised to do better on the next winetest run.
Greg.