I stumbled on a little bug today while trying to use my Sennheiser USB headset adapter with my Sennheiser headphones. I plugged them in and got nothing...
The device would appear in System - Preferences - Sound, but on the available output tab it didn't show.
A bit more probing found that Alsa worked just fine with it.
Finally I determined that Pulseaudio wouldn't fully recognize the headset after it was plugged in until it was restarted. To do this you can either log out and log back in or type in the following commands at a console:
pulseaudio -k pulseaudio --check
Be sure you don't have any software open that's using the speakers or mic at the time or that program will likely freeze up.
If you've installed Ubuntu 10.04 you may have noticed that it boots amazingly fast, but on some installations the time after you login until the desktop is visible may take 5 to 10 seconds.
I found that there were several startup applications by default that I had no need for. Disabling those applications will cause your desktop to be available nearly instantly, meaning with the new improved boot times, I can actually turn on my computer and be sitting at a working desktop in about 7 seconds (not counting BIOS post time of 23 seconds.)
And that's not a resume - that's a fresh boot.
How do you do that last bit of speedup? After logging into Ubuntu, go to System - Preferences - Startup Applications.
Here's a list of what I disabled, your mileage may vary:
Bluetooth Manager (I don't have a bluetooth device in this PC) Evolution Alarm Notifier (I run Thunderbird) Personal File Sharing Remote Desktop Server Ubuntu One Visual Assistance
In addition to doing that, I added in a few other programs such as Rhythmbox to start when I log in. Even with those extra apps added, it shaved several seconds off my login time.