OK, I think I found the mute problem, but again, not 100% sure if this is whats causing it:
The mixer seems to be getting closed BEFORE the line is unmuted in the shutdown sub. This would cause the DoMute call to happen on the default sound card, which would infact mute, rather than unmute.
Think that would solve the muting problem?
If hMixer <> 0 Then mixerClose hMixer: hMixer = 0
The line above needs to be called AFTER this line:
'UMute Sound (if we muted it)
If ExitMute And Not VOICE_ON Then DoMute MasterVolMap
I'm guessing the above comment is meant to say "UnMute" not "UMute" too.
EDIT: I added the line "ExitMute=false" to RR.ini (second instance) and it fixed the problem, because of course neither of those mute commands on shutdown would be called. So that just convinces me more that the above lines are indeed causing the bug.
Should I start another thread re: the multi-instance video issues?