ubuntu wep problem

HELP
i have problem connecting to my university wireless network
i connect but after a period of time(3-5min) i no longer can surf the
pages or anything(and network monitor says that the ap and my comp are
transmitting packages one to another)
i have ubuntu 5.10, ralink rt2500 pcmcia wireless card and im using
xsupplicant to authenticate and dhclient to get ip adress

the way i connect to net:
$iwconfig ra0 essid FERwlan
$iwconfig ra0 key open
$ifconfig ra0 up
$xsupplicant -i ra0
$iwconfig ra0 key open (because xsup 1.2.4 changes it back to
something else)
$dhclient ra0 (after i get authenticated by xsup)

xsup config is ok because my friend with fc5 and intel centrino platform
gets normaly connected to wireless netowork and has no probelms

if i then after i can no longer surf pages kill xsup and then load it
again, i can again surf pages for about 3-5min

what to do???