The problem occurs when applications output audio. I've narrowed this down by running the applications ie vlc in console mode with only audio output. When playing videos with audio disabled I am able to play through an entire 1 hour movie. With audio enabled the system locks up every time. I've tried everything I could think of to get it working.

2.6.18-5-k7 #1 SMP
Debian etch

description: Motherboard
product: A7V8X
vendor: ASUSTeK Computer INC.
physical id: 0
version: REV 1.xx
serial: xxxxxxxxxxx

lspci -v:
00:11.5 Multimedia audio controller: VIA Technologies, Inc. VT8233/A/8235/8237 AC97 Audio Controller (rev 50)
Subsystem: ASUSTeK Computer Inc. A7V8X Motherboard (Realtek ALC650 codec)
Flags: medium devsel, IRQ 185
I/O ports at e000 [size=256]
Capabilities: [c0] Power Management version 2

lsmod:
snd_via82xx 26776 1
snd_ac97_codec 88036 1 snd_via82xx
ac97_bus 2688 1 snd_ac97_codec
snd_pcm_oss 39712 0
snd_pcm 69444 4 snd_via82xx,snd_ac97_codec,snd_pcm_oss
snd_page_alloc 9992 2 snd_via82xx,snd_pcm
snd_mixer_oss 16000 1 snd_pcm_oss
snd_mpu401 8040 0
snd_mpu401_uart 8512 2 snd_via82xx,snd_mpu401
snd_seq_dummy 4292 0
snd_seq_oss 30464 0
snd_seq_midi_event 7488 1 snd_seq_oss
snd_seq 46736 5 snd_seq_dummy,snd_seq_oss,snd_seq_midi_event
snd_timer 20996 2 snd_pcm,snd_seq
snd_rawmidi 23072 1 snd_mpu401_uart
snd_seq_device 8140 4 snd_seq_dummy,snd_seq_oss,snd_seq,snd_rawmidi
gameport 14920 2 snd_via82xx,analog
snd 49124 14 snd_via82xx,snd_ac97_codec,snd_pcm_oss,snd_pcm,snd_mixer_oss,snd_mpu401,snd_mpu401_uart,snd_seq_dumm y,snd_seq_oss,snd_seq,snd_timer,snd_rawmidi,snd_seq_device
soundcore 9568 1 snd

Is any information being written to the logs (/var/log/messages, etc.)? Are you using KDE/artsd (I don't have a Debian box installed to check what runs by default)? If so, the info here might help.

I solved the issue after much misdiagnosing..
I reduced the multiplier for my cpu and the issue went away.

Thanks for posting how you fixed it