I too use wicd and noticed similar behaviour.
The user interface to wicd showed me many networks
to connect to, and (unlike others) it does not automatically
remember a preferred network to connect to like other network
manager GUIs.
What I'd suggest is, de-select all "pre-selected" networks within
wicd (for me, it would try to auto-connect to the first network
listed/detected).
Then, find the network that you do want to connect to by default,
and before choosing it, enter the properties tab for that specific connection.
From a somewhat old MEPIS doc page.. hopefully the directions still apply..
(fingers-crossed).
"To connect to the same SSID, open the program, click on the triangle
next to the SSID you want, and check "Automatically connect to this
network."
http://www.mepis.org/docs/en/index.php/Wicd