Wireless PCI card often got lost in Ubuntu after waking up from Suspend mode. Network-manager is rather useless and non intuitive. To fix this , edit /etc/default/acpi-support
# Add services to this list to stop them before suspend and restart them in
# the resume process.
STOP_SERVICES="networking"
updated: 13 feb 2007: this doesn't really solve the problem. the wlan still got lost after suspend. :( Now experimenting with Wicd.