Network-manager problems

[Joep L. Blom]

I'm in a catch-22 situation!
I have installed -on a laptop - Karmic and it runs OK, except..
network-manager(as usual??) doesn't like wireless. After installing - 
from a USB-stick - the Broadcom drivers and some changes in 
/etc/network/interfaces NM sees my wireless even connects and get an 
IP-address from the DHCP server. Sο far so good! and when I don't 
connect or do anything the connection stays on.
However, when I make a connection and e.g. try to lookup a page, then 
after <1 minute the connection is broken and NM says I'm off-line.
Looking in the syslog I see every 2nd minute the following message:
Oct 30 12:13:35 laptop wpa_supplicant [1100]: CTRL_EVENT_SCAN_RESULTS
Oct 30 12:15:35 laptop wpa_supplicant [1100]: CTRL_EVENT_SCAN_RESULTS
and suddenly:
Oct 30 12:28:43 laptop wpa_supplicant [1100]: CTRL_EVENT_DISCONNECTED - 
Disconnect event - remove keys
followed by:
Oct 30 12:28:43 laptop NetworkManager: <info> (wlan0) supplicant 
connection state: completed -> disconnected
Then a lot of messages as wlan0 is trying to come up again and suddenly 
kernel messages tell the device is up again but it is apparently looking 
for IPv6 routers - which of course aren't available - and NM says that 
wlan0 is disconnected.
I hope somebody has an explanation and if anybody knows a solution.
(install wicd is not an option as I cannot connect to the Internet!!)
Hope somebody can shed some light in this problem.
Joep