I also can't set the ESSID unless I'm in Ad-hoc mode. Strangely, each time I set the essid in ad-hoc, the AP MAC address appears to change randomly. Of course, I'd like to run in Managed mode without WEP, but I can't set the ESSID doing this (I've tried turning on wep, then setting essid, then turning off wep, and setting again, but no luck).
Also, 'iwlist wlan0 scan' doesn't show anything.
I'm using the Broadcom 94306 chipset. The wap is only 802.11b, but the Broadcom is 802.11g.