How odd - I haven't seen that on any of my ubuntu laptops. Are you using
a windoze driver with ndiswrapper? What sort of wireless hardware do you
have?

I have a Linksys ADSL WiFi router and a locally built laptop with dualcore
Intel. There seems to be no ndiswrapper loaded as these two ndiswrapper-common
and ndiswrapper-utils-1.9 packets are not checked in the Synaptic packet
management screen.

Thanks I got also this :
https://help.ubuntu.com/community/WifiDocs/WirelessTroubleShootingGuide
jcglt

Refering to
https://help.ubuntu.com/community/WifiDocs/WirelessTroubleShootingGuide para 6.1
Dropped connections I may have found an answer to my problem : interference with
other wireless devices in my home or in neighbors' home as I am living in a
multi apartments building.
Another reason to think that : my WiFi has been running without disconnections
between 10 and 12am today, nobody around and probably nothing to be disturbed
from. Yesterday evening, with all neighbors at home and probably a lot of
appliances running it disconnected every five minutes then, due to this nice
"wicd 1.6.1" reconnected automatically.

I have a better understanding of my problem :
- on Windows XP I detect 3 WiFi routers in my neighborhood ;
- with Ubuntu Karmic :
. wicd detects 4 WiFi routers (3 on Channel 11 and 1 on channel 1)
. wifi-radar detects 5 routers (3 on ch11 and 2 on ch1).
As I am set on channel 11 I'm facing interference from 2 other routers and
according to WiFi documentation I could read there should be a 5 digit
separation between two closely used channels to avoid interference. I should try
to set my router on 6 and will look more deeply in the documentation.
Sorry for this long discussion, in which Ubuntu has probably nothing to do,
being probably more sensitive than Windows XP facing interferences.
Thanks for the answers and help I got.

What sort of wireless hardware is in your laptop?

What sort of wireless hardware is in your laptop?

could there be a restricted driver for your wifi from the manufacturer
system /adminsitration /hardware drivers?