Wireless Multicast reception

I thought I'd ask this question here first, since my platform is
Angstrom on Beagle,
and I know the first thing the Linux-wireless people will say to do is
to upgrade my kernel.
Hopefully someone here can give me a clue.

I've got Angstrom (2.6.32 kernel - probably 3-4 months old) on a
Beagle C4. I'm using
a wireless USB adapter (rt73usb driver). Everything works just fine,
except that I cannot
receive multicast data. I can send it out just fine, and other
systems on the net receive
my multicast transmissions, but I never see any multicast from anyone
else. The same
multicast application works just fine over a wired connection (asix
based adapter).

ifconfig and iwconfig both report the device is up and operating in
multicast mode.

I'm wondering if anyone knows if there is anything special I need to
do to get this to work.
I've tested other devices on the same wireless network, so it's not
the AP preventing things
from working, but it seems like it's something in the kernel itself.

Thanks,
Pete