system freeze when playing videos

Binary package hint: pulseaudio

The system freeze 5 times in the last 2 days when I was playing videos.
Keyboards leds (NumLock CapsLock ScrollLock) start blinking.

I reported this bug to pulseaudio because last messages from syslog are:
Oct 1 02:15:10 tyrael-ion pulseaudio[1628]: ratelimit.c: 130 events suppressed
Oct 1 02:15:39 tyrael-ion pulseaudio[1628]: ratelimit.c: 17 events suppressed

ProblemType: Bug
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: NVidia [HDA NVidia], device 0: ALC662 rev1 Analog [ALC662 rev1 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: tyrael 1577 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'NVidia'/'HDA NVidia at 0xfae78000 irq 23'
   Mixer name : 'Nvidia MCP7A HDMI'
   Components : 'HDA:10ec0662,19daa108,00100101 HDA:10de0007,10de0101,00100100'
   Controls : 29
   Simple ctrls : 16
Date: Thu Oct 1 02:32:41 2009
DistroRelease: Ubuntu 9.10
NonfreeKernelModules: nvidia
Package: pulseaudio 1:0.9.18-0ubuntu3
ProcEnviron:
 PATH=(custom, user)
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-11.36-generic
SourcePackage: pulseaudio
Uname: Linux 2.6.31-11-generic x86_64