Description:

In the last days my sound failed twice. That's not usual. I saw this phenomenon earlier but probably it happened once in 3 or 4 months. Now it happened already twice a week. At the first time in the volume control of Gnome I only had one volume switcher left. I think it was the microphone switcher. All the other switchers were gone. Usually I have switchers Master, Headphone, PCM, Line-in,.... but they all were gone. After rebooting twice, the sound went back (Yes, I had to reboot twice to bring the sound back). At first I thought it has to do with the fact, that I didn't rename the sound config file in /etc/modprobe.d/ to sound.conf (because sound instead of sound.conf is deprecated). But this wasn't the cause.
I'm not sure if it's a coincidence, but I noticed the phenomenon every time when I wanted to watch youtube-videos. It never apeared before when I listened to mp3s.
As I rebooted I saw some gnome messages and one messages was something like this: alsa-core.c 324 File or Directory not found (I'm not sure if File or Directory not found is right, but at any rate, alsa-core.c 324 is right).

Additional info:
My sound device:

description: Multimedia audio controller
product: 82801BA/BAM AC'97 Audio Controller
vendor: Intel Corporation
physical id: 1f.5
bus info: pci@0000:00:1f.5
version: 12
width: 32 bits
clock: 33MHz
capabilities: bus_master
configuration: driver=Intel ICH latency=0
resources: irq:17 ioport:dc00(size=256) ioport:e000(size=64)

$ cat /proc/asound/cards
0 [I82801BAICH2 ]: ICH - Intel 82801BA-ICH2
Intel 82801BA-ICH2 with ALC200,200P at irq 17
1 [UART ]: MPU-401 UART - MPU-401 UART
MPU-401 UART at 0x330, irq 5
2 [U0x46d0x9a1 ]: USB-Audio - USB Device 0x46d:0x9a1
USB Device 0x46d:0x9a1 at usb-0000:00:1f.2-2, full speed

$ cat /proc/asound/modules
0 snd_intel8x0
1 snd_mpu401
2 snd_usb_audio

extra/alsa-lib 1.0.21.a-1
An alternative implementation of Linux sound support
extra/alsa-oss 1.0.17-1
OSS compatibility library
extra/alsa-utils 1.0.21-1
An alternative implementation of Linux sound support
extra/alsaplayer 0.99.80-2
A heavily multi-threaded PCM player that tries to excercise the ALSA library and driver quite a bit.
extra/gnome-alsamixer 0.9.6-3
Gnome ALSA mixer
extra/wmix 3.1-4
Dockapp mixer for OSS or ALSA

extra/flashplugin 10.0.32.18-1.1
Adobe Flash Player

Steps to reproduce:
It seems that it has to do with watching youtube videos (Buggy Flash-Plugin?)