WLAN stops working when idle

[Leonardo M. Ramé]

I have noted that my wlan stops responding when the O.S. does not use the network for a while (10 minutes aprox), and I have to do "ifconfig wlan0 down && ifconfig wlan0 up && dhclient wlan0" to reconnect.

The network card is the internal Wi-Fi from my Dell Inspiron 1525, and uses ndis to wrap the WinXp driver.

/etc/rc.conf:
...
wlans_ndis0="wlan0"
ifconfig_wlan0="WPA SYNCDHCP"
wpa_supplicant_enable="YES"
...

/etc/wpa_supplicant.conf

ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=wheel
ap_scan=1
network={
	ssid="strada"
	key_mgmt=WPA-PSK
	psk="martin13"
}

uname -a:

FreeBSD inspiron-1521 8.1-RC2 FreeBSD 8.1-RC2 #0: Tue Jun 29 20:42:40 UTC 2010     root at almeida.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386


Any hint?

Leonardo M. Ramé
http://leonardorame.blogspot.com