Sound problem?... or?

[Curt Tresenriter]

I have always found sound under Ubuntu to be problematic at worst under
many different versions beginning with Warthog but always found some
solution when a problem cropped up. 
Pulse made things more difficult, once I could only resolve the issue by 
removing pulse altogether - not sure which release that was. Most of the
time it "just worked" and pulse hasn't posed any problems for some time now.

I don't think pulse is the problem here but I'm not really sure.

Here's what happened.

I removed my Asus Xonar XD soundcard a couple days ago and replaced it
with the M-Audio 2496.

At the time I only tried to play audio using VLC and it worked with no
problems.
The next day I discovered that audio would not play when watching a
youtube video. I then looked at sound settings and found the card did
not show under 'Output' but it was under 'Input' and 'Hardware'.
Youtube hadn't been a problem before the sound card change.

Testing further I found that there was no sound in exaile player,
rhythmbox, amarok, xine or movie player nor could I get audio from the
player software on my Synology NAS. Nothing except VLC would play
audio and it worked each time I tried it.

Eventually I found that when I switch users to the guest account the
card was displayed and sound worked normally with youtube.
I didn't bother getting permissions set properly to access my local
music in order to test that from the guest account.
After going back to my user account once, then back to the guest
account the card was no longer showing in sound settings at all when
logged in as guest, not in output, input or hardware.

In addition, suddenly this morning the mouse wheel would no longer
scroll web pages in Firefox and it would not respond when clicking
history, tools, bookmarks, etc. This problem was not present in
Chromium and only showed up after a few minutes of troubleshooting, it
did work in Firefox first thing today. After getting sound back this no
longer occurred.

Next I logged in choosing Gnome session and found all sound works normally.

I had previously been testing using Gnome Classic session which I think
was the default or at least it was what I had been using before the
sound card swap, "Gnome Classic (no effects)" session also produced no
sound.

I'm not sure what session was the default before I replaced the sound
card but there was never a problem of any kind related to sound in many
months since installing UbuntuGnome, only after trading sound cards.

Now (after getting sound working properly again), when I switch users to
the guest account (after being logged in to the Gnome session) the
cards has disappeared altogether from the guest account sound settings.

Another strange thing (I think) is that although I understood that
pulseaudio could not play two sound sources at the same time (this may
be outdated info), this morning with music playing from the NAS, I
opened VLC to play an album and a dialog box popped up telling me:
"Audio output failed:
The audio device "sysdefault:CARD=M2496" could not be used:
Device or resource busy." 
it then immediately began playing the album I chose.

Now, with both the NAS and VLC playing I opened and began playing
another album in Rhythmbox and another in exaile and another in Amarok.
All four playing four different files at the same time with no
complaining except for the VLC message.

I don't know if any of this might be a bug or if it's all quite normal
though if so, I do not understand why the sound card disappeared from
the Guest session or why choosing the GNOME session allowed audio to
play but the others wouldn't.


I would appreciate if anyone could shed any light on this issue for me.