I have the same issue. Further details:
*running on a pandaboard ES
*dhcpcd works just fine with Ethernet on eth0
*stock image works fine with eth0 and wlan0, but wlan0 breaks after updating packages
*in order to get wireless to work at all, i have to rebuild the ti-connectivity package (even the june 12, 2012 package doesn't include the necessary firmware)
I realize that this thread is in the rpi forum and I'm using a pandaboard, but the issue is too similar to ignore.