For ubuntu 8.04 and perhaps other versions on Dell Inspiron 1501 edit /etc/default/acpi-support and set this line as follows (the quotes were empty “” when first opened). A reboot was necessary.

STOP_SERVICES=”networking nm-applet”

Fix courtesy of Brian Pibris, who in turn found it here http://boulderjams.wordpress.com/2007/02/20/ubuntu-dell-suspend-fix/