I noticed that, when I unplugged my laptop, or closed/opened the lid, my wireless connection dropped, every time.
I tracked it down to
pm-powersave, and made it stop, see below.
This could also cause repeated requests for network passwords.
I've found that
/usr/sbin/pm-powersave turns OFF my wireless card when I switch to battery or suspend by closing the laptop's lid. I've gotten wireless to stay up between hibernates by executing
sudo /usr/sbin/pm-powersave false. The
man pm-powersave page says I can create an empty file
/etc/pm/power.d/wireless to prevent
/usr/lib/pm-utils/power.d/wireless from running and doing its magic. I've done it, and it works for me.
I found this by doing an
ls -lrt /var/log just after the event, and looking at the last 100 so lines of the recently modified logs. I use this technique to start answering many questions about what my system just did.