Found another quirk: answered a post quoting, in the message composition form the quoted part was black text on dark grey background, unreadable without highlighting it with the mouse.
Once posted it was OK again and up until now it happened only once anyway, I don't know what happened...
Edit: Another possible bug, the post button every now and then doesn't work at the first click, particularly using the "quick reply" form. And the unrecoverable FF freezes I experienced all happened this way with this event sequence: first click on "Post", nothing happened, second click freeze (most probably Flash related, as in the old VGC similar events were solvable, under linux, without closing FF, but simply killing the process "npviewer.bin", now, when it happened in VGC 2.0, "npviewer.bin" became unkillable and it was necessary to kill FF and restart it).