Mac OS X just hit 10.3.8, but I'm still having problems with changes introduced in 10.3.7:

M-Audio interfaces' latest drivers appear to cause incompatibility with
the new OS; my Duo and FireWire Solo both stopped receiving and sending
audio signal (though they appear normally) after the update. With the
Solo, rolling back to the previous driver version 1.4 (also on the
M-Audio site) fixed the problem, though with the Duo I'm stuck for the
moment. (There's a trick to getting the old version: when looking for
drivers on their site, don't specify your OS, just your hardware.)

I'll update you if I learn anything — other audio hardware here at CDM HQ appears to be unaffected.

At least all those Windows XP security updates aren't doing anything.