Brains working towards machine consciousness

My machine developed an interesting 'issue' a little while ago.  For some reason, it decided I didn't want to hear anything I tried playing in Windows Media Player - other apps would play OK.  I am not sure what caused it, but I did find a way to get the sound back in WMP today.
Yesterday I was looking at the Audio control panel - and I noticed that if I went into the (so-called) advanced settings, that it was showing the mute-all button was selected.  Now, that sounds like a simple user error, right?  But it wasn't.
If I double click on the audio button in my system tray, that showed the mute-all as not being selected - which is what I had been looking at before.  So, now I de-selected the mute-all, and got sound, as one might expect.  But when I closed the audio properties dialogue, the sound went off again - and sure enough, if I re-opened it, the mute-all checkbox was re-selected.  This was (irritatingly) reproducible.
Remembering that the mute-all had not shown up on when I accessed the dialogue in my normal way, I opened it for comparison (suddenly wondering whether it showed the same controls).  When I then closed both the volume setting dialogue boxes, the problem was resolved.  So now I have sound back.
I am not sure what was automatically muting my sound for me, but having both boxes open appears to have resolved the issue.