[amd64] pcm0 dies after a while

I've been plagued with this problem for the last week or two now. 
Constantly upgrading, tweaking, in the hopes of finding relief, but so
far, none.

pcm0 will work fine for a while, then suddenly, any further attempts to
use it generate the following:

Jul 13 23:31:18 dolphin kernel: pcm0:play:0: play interrupt timeout,
channel dead
Jul 13 23:31:49 dolphin last message repeated 10 times

Madplay, mpg123, etc. will start, play a fraction of a second's worth
of sound, and then exit.

This continues until a reboot.  The device is completely unusable until
then.

$ cat /dev/sndstat
FreeBSD Audio Driver (newpcm)
Installed devices:
pcm0: <Nvidia nForce3> at io 0xe800, 0xec00 irq 10 bufsz 16384 
(1p/1r/0v channels duplex default)

-- 
Conrad J. Sabatier <conrads_at_cox.net> -- "In Unix veritas"