No transmission between AP and clients

[vcuirassier at epsi.fr]

Hi all,

I use the Netgear MA401 PCMCIA card and HostAP-2002-10-12 to make a Linux 2.4.18
based access point.

Everything seems to be correctly configured: the card is supported, the cardmgr
daemon launches hostap_cs after insertion and creates the wlan0 device (Master
mode). Then I assign an address to wlan0, and start the dhcp daemon on that
interface.

Clients can enter the wireless network (getting an address from dhcpd), but when
they ping the access point they don't get any reply, even if tcpdump shows
incoming ICMP ECHO requests. SSH and HTTP connections fail the same way. I don't
filter anything in the IP layer, so it can't be Netfilter that silently drops
packets.

Can anybody think of a possible reason for this problem?