I've got a fiendish dell 500m running mdk 9.2pwp, problem is, while I am connected to the wireless network, I am unable to open any filemanager, and the second i write ifdown wlan0, the problem disappears. As an extra note, I am running the ndiswrapper to control the wlan card, I'm running an older version (0.4) but I am hesitant to upgrade it due to the fact that it works now. Any help is helpful (I think)

check /etc/resolv.conf and make sure that you have a valid nameserver entry (either a real nameserver or your gateway/router)

Also check /etc/sysconfig/network-scripts/ifcfg-wlan0
and make sure that these are defined

GATEWAY=192.168.1.1
NETMASK=255.255.255.0
BROADCAST=192.168.1.255

You will change 192.168.1 to your network.

my resolve.conf consists of :

search adsl.no local
nameserver 127.0.0.1
nameserver 192.168.0.1

my ifcfg-wlan now consists of

DEVICE=wlan0
BOOTPROTO=dhcp
NETMASK=255.255.255.0
BROADCAST=192.168.1.255
GATEWAY=192.168.1.255
ONBOOT=no

Now what

by the way, kde will not start after a serverkill with the wlan on (same problem I presume)

/etc/resolv.conf should just be
nameserver 192.168.0.1

given that 192.168.0.1 is your gateway/router and can pass thru DNS information to clients.

DEVICE=wlan0
BOOTPROTO=dhcp
NETMASK=255.255.255.0
BROADCAST=192.168.0.255
GATEWAY=192.168.0.1
ONBOOT=yes

Also make sure that the filename is ifcfg-wlan0 and not ifcfg-wlan

You can also look at ifup-wireless in the same directory for wireless parameters that you can set, so you would never have to set anything by hand when the machine boots up.

example
ESSID=myessid
CHANNEL=6
KEY="restricted [1] XXXXXXXXXX"