In previous posts, I tried fixing error messages that I was getting in a Windows XP virtual machine (VM) running on VMware Workstation 6.5.2 on Ubuntu Linux, version 9.04. I didn't know, at that time, whether some of my problems stemmed from having done an upgrade rather than a clean install of Ubuntu. Now I found myself facing the same problem again, after a clean install of both Ubuntu 9.10 (Jaunty Jackalope) and VMware Workstation 7.
The problem was as follows: if I checked the "Connect at power on" option, then audio would not run in the VM until (in full screen mode) I went into VM > Removable Devices > Sound Card > Connect; but when I did that, I would get this error message:
Failed to open sound device /dev/audio: Device or resource busy. Failed to connect virtual device sound.
One recent discussion seemed to suggest that the problem was that Flash Player and/or Alsa audio. I suspended my VMs and rebooted the computer. When it rebooted, I made sure that Firefox was not running. I resumed the VM and audio played OK in IrfanView. I started Firefox inside the VM (i.e., in Windows XP) and played a YouTube video. The audio was still OK in IrfanView. I started a second session of Workstation and resumed a different VM in that session. The manual sound card connection went OK; and there, too, I could play audio without stuttering. The audio in the second VM was not as good; it had some static.
With those two VMs open, I started Firefox in Ubuntu (i.e., not in a WinXP VM). I played another YouTube video. Now I got an error message, and audio would not play in IrfanView within the VM. I tried the other VM; same thing. The error message was "Failed to open sound device /dev/audio: Device or resource busy. Sound will be disconnected." I went back to Ubuntu and killed Firefox. Now I was able to connect the sound card and play audio inside the two VMs, same as before, complete with mini-stutters in the second one. I started Firefox again in Ubuntu. The audio was still OK inside the VM. If I was playing audio in IrfanView in the VM and then went into a YouTube page in Firefox, the audio would not play in the latter. I had to restart Firefox to get its YouTube audio to play, and then, as before, I was not able to hear audio inside the VM. It worked the same way if I played a YouTube video in Opera rather than in Firefox. So it seemed that the problem (which has apparently been around for years) continued to be within VMware Workstation.
For the time being, the solution seems to be either (a) to watch videos and other webpages that use Flash, do it in a browser session that is running inside your VM, not in a browser running in Ubuntu, or (b) after watching a video or otherwise using Flash in Ubuntu, kill the program that used it (e.g., Firefox) and manually reconnect with your sound card inside the VM.