I'm having the same problems, can't get AP mode working on my DWA-556 card. I've tried using madwifi (trunk, v0.9.4), but the NIC won't send out any packets after a client computer connects to it.
According to a page at Linux Wireless hostapd is required for AP mode, but hostapd gives me the following errors when run:
# hostapd -dd /etc/hostapd/hostapd.conf
Configuration file: /etc/hostapd/hostapd.conf
ioctl[PRISM2_IOCTL_PRISM2_PARAM]: Operation not supported
Could not enable hostapd mode for interface wlan0
hostap driver initialization failed.
wlan0: Unable to setup interface.
Flushing old station entries
Deauthenticate all stations
I'm hoping someone can shed some light regarding this, thanks in advance!
bridge=br0 # eth0 and wlan0 are bridged