Problems with chipset AT76C505a

Hello,
 Using the Berlios driver with Fedroa Core 3, I experiment some problems I
didn't have before. Actually, the driver worked for some days, even at
boot (automatically detected thanks to ifcfg-wlan0 script), and a green
LED switched on to say the card was scanning and working.
 But now, this LED doesn't want to come back and it's impossible to join
the network. I have a ping response on my card (it's a internal USB card)
but tcpdump on wlan0 say nothing pass.
 Here is the error I've got when I plugged the card :

ip_tables: (C) 2000-2002 Netfilter core team
/drivers/wifi/at76c503a/at76c503.c: wlan0: tx timeout.
usb 3-2: events/0 timed out on ep0in
/drivers/wifi/at76c503a/at76c503.c: wlan0: get_cmd_status failed: -110
/drivers/wifi/at76c503a/at76c503.c: wlan0: tx timeout.
/drivers/wifi/at76c503a/at76c503.c: wlan0: tx timeout.
/drivers/wifi/at76c503a/at76c503.c: wlan0: tx timeout.
usb 3-2: events/0 timed out on ep0out
/drivers/wifi/at76c503a/at76c503.c: wlan0: set_card_command(CMD_RADIO)
failed: -110
/drivers/wifi/at76c503a/at76c503.c: wlan0: tx timeout.
/drivers/wifi/at76c503a/at76c503.c: wlan0: tx timeout.
usb 3-2: events/0 timed out on ep0out
/drivers/wifi/at76c503a/at76c503.c: wlan0: set_mib (preamble) failed:
-110
usb 3-2: events/0 timed out on ep0out
/drivers/wifi/at76c503a/at76c503.c: wlan0: kevent: start_scan failed
with -110

[root@localhost ~]# lsmod | grep at
at76c505a_rfmd2958     40964  0
at76c503               84704  1 at76c505a_rfmd2958
at76_usbdfu             5508  1 at76c503
battery                 9285  0

[root@localhost ~]# iptables -L
ip_tables: (C) 2000-2002 Netfilter core team
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

I don't remember having done something on my network configuration so I
don't understand this regression :-(
Did somone meet the same problem ? Did someone have a clue ?
Thanks
Steve