Titi says its already known, that MG64 3.12 chrashes on windows on exit after being online in Masterserver-lobby. He suspected that this an issue of WIN 10. But its happening on WIN7 64 too.
Its enough to visit the Masterserver-Lobby omce to get a crash on exit (after closing opengl-screen).
After an onlinegame with Titi yesterday I got an errormessage on exit which I show below. Maybe its just something with IRC? Other crashes on exit showed no messages.

Greetz nig.