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.