Looping sound output from pcm

I ran aim after a recent kernel update, and had a rather odd problem.  I
got an instant message from someone which resulted in a "ding" from aim. 
However, the ding never stopped dinging -- the sample repeated over and
over again, and continues as I type.  Even after the aim process exited. 
Sending additional sound output didn't make it go away either.  KDE/arts,
etc, don't seem to be involved in the problem, so it really seems like the
kernel is looping the sample.  When I try to unload pcm, I get: 

pcm0: unregister: channel pcm0:play:2 busy (pid 965)

And there's no pid 965.

paprika# cat /dev/sndstat 
FreeBSD Audio Driver (newpcm)
Installed devices:
pcm0: <ESS Technology Maestro3> at io 0xd800 irq 5 (4p/1r/0v channels duplex default)

Any suggestions welcome; in the mean time, I'll just listen to it ding
away ad naueseum. 

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert_at_fledge.watson.org      Senior Research Scientist, McAfee Research