routing problems on wireless

when my wireless card comes up, if i bring it up with either ifup or knetworkmanager it fails to add required routing information despite the fact that said info is in the routing config file /etc/sysconfig/network/route and/or ifroute-wlan0. So i have to add the routes manually

route add -host dev wlan0
route add default

if i do the above after i bring up wlan0 with knetworkmanager it works ok but if i put the route info in when i bring wlan0 up with ifup every attempt to connect to a website fails after a lengthy timeout. any idea why? and why does knetwrkmanager ignore th route files?