For quite a while I have been having a recurring problem with sound on a Windows guest OS under Virtualbox. After a while it will just hang up and when I restart the Virtualbox session under Ubuntu I will get an error message saying that the host’s sound system isn’t working. Since I don’t use Virtualbox that often I forget about it and moved on.
I know it has something to do with the Pulseaudio system on my Ubuntu set up but was a bit lazy to google for a solution. Anyway my sound was quite fine under Ubuntu so I didn’t mind it at all.