I, too, encounter this problem after my machine (running Ubuntu 12.04, gnome, fully patched) has been running several days, with at least one suspend/resume per day.
It's not troubling enough to me to reconfigure gnome, so I've instead implemented a daily cronjob to reload nm-applet. However, it would be nice to get this fixed, since it's most probably a buffer overwrite or similar someplace.
One caveat for our less-experienced correspondents: nm-applet is in /usr/bin, so './nm-applet &' above will work only if your working directory is /usr/bin. A more general solution is 'nm-applet &'.
I'll probably be upgrading to 12.10 this weekend. so I'll report back if this problem is fixed in 12.10.
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