I have played with this on and off for the last 18 months. Lenovo laptop with Slack 12.1 and whatever WICD version the Slackbuild site tells you to use with 12.1. I have found two problems:
1. Something in the stack sometimes falls over if I put my laptoop to sleep and then re-start
2. dhcpcd fails to get an IP address because it thinks it already has one
I now solve both of these problems (when they occur, which is not always and a bit random) by doing the following:
1. Remove and re-install the driver for my wireless card
modprobe -r iwl3845
2. Re-start WICD
That nearly always seems to cure things. Very occasionally I also need to do
iwconfig wlan0 ap any
when accessing some new network and the iwconfig is set up for my home network with its password etc, but sometimes wicd seems to take care of all that itself.
All of these operations have to be done as root of course.