Sound partly broken until reboot

[Wolfgang Pfeiffer <roto@gmx.net>]

Hi

I had to reboot to get sound working again on a Powerbook G4
in Gnome 2.4

Kernel is 2.4.22-ben2

OS is 3.0.r1 testing/unstable

cpu             : 7455, altivec supported
clock           : 867MHz
revision        : 3.2 (pvr 8001 0302)
bogomips        : 864.64
machine         : PowerBook3,5
motherboard     : PowerBook3,5 MacRISC2 MacRISC Power Macintosh
board revision  : 00000000
detected as     : 80 (PowerBook Titanium IV)
pmac flags      : 0000000b
L2 cache        : 256K unified
memory          : 768MB
pmac-generation : NewWorld

xmms, mplayer: nothing; I found only the error sound at the shell
prompt (xterm) worked.

I re-logged into X, making sure the sound server is enabled in Gnome
(Applications --> Desktop Preferences --> Sound): nothing.

I checked whether audio was blocked by another process doing
fuser -v /dev/dsp
But nothing that was going on at /dev/dsp.

kern.log, if I chose the correct log for the situation, told this:
--------------------------------------------------------
ct 31 18:46:35 debby kernel: end_request: I/O error, dev 16:00 (hdc),
sector 0
Oct 31 18:46:35 debby kernel: hdc: command error: status=0x51 {
DriveReady SeekComplete Error }
Oct 31 18:46:35 debby kernel: hdc: command error: error=0x54
Oct 31 18:46:35 debby kernel: end_request: I/O error, dev 16:00 (hdc),
sector 4
Oct 31 18:46:35 debby kernel: hdc: command error: status=0x51 {
DriveReady SeekComplete Error }
Oct 31 18:46:35 debby kernel: hdc: command error: error=0x54
Oct 31 18:46:35 debby kernel: end_request: I/O error, dev 16:00 (hdc),
sector 8
Oct 31 18:46:35 debby kernel: hdc: command error: status=0x51 {
DriveReady SeekComplete Error }
Oct 31 18:46:35 debby kernel: hdc: command error: error=0x54
Oct 31 18:46:35 debby kernel: end_request: I/O error, dev 16:00 (hdc),
sector 12

 [ ... cut ... ]
-------------------------------------------------------------

In the end I was fed up with the crap, rebooted, and sound was working
again (except mplayer still happily refusing to play a .mov [Matrix
trailer] file)

Any ideas, how to fix a situation like this without rebooting?

Thanks in anticipation

Regards,
Wolfgang