Comment 49 for bug 356152

It is affecting me too.
When I killall update-notifier then start a new one, the notification aera blinks once, but no icon or anything appears. Hope this helps:

./auto.pl
4 normal updates, 0 security updates available
interval_days from gconf: 7
last_launch from gconf: 1270623944, Wed Apr 7 09:05:44 2010
mtime from /var/log/dpkg.log: 1270624167 Wed Apr 7 09:09:27 2010
ctime from /var/log/dpkg.log: 1270624167 Wed Apr 7 09:09:27 2010
mtime from /var/log/apt/term.log: 1270624168 Wed Apr 7 09:09:28 2010
ctime from /var/log/apt/term.log: 1270624168 Wed Apr 7 09:09:28 2010
latest previous update: 1270624168,ctime /var/log/apt/term.log
time now 1270722519 Thu Apr 8 12:28:39 2010, delta 98351
It's been 1.13832175925926 days since last update.
Autolaunch disabled. There has already been an update within the last 7 days (1270624168,ctime /var/log/apt/term.log)

update-notifier --debug-updates
(update-notifier:5596): update-DEBUG: update_check()
(update-notifier:5596): update-DEBUG: /usr/lib/update-notifier/apt-check returned 4 (security: 0)
(update-notifier:5596): update-DEBUG: is_package_system_locked: 0
(update-notifier:5596): update-DEBUG: interval_days from gconf: 7
(update-notifier:5596): update-DEBUG: last_launch from gconf: 1270623944 (Wed Apr 7 09:05:44 2010)
(update-notifier:5596): update-DEBUG: mtime from /var/log/dpkg.log: 1270722822 (Thu Apr 8 12:33:42 2010)
(update-notifier:5596): update-DEBUG: ctime from /var/log/dpkg.log: 1270722822 (Thu Apr 8 12:33:42 2010)
(update-notifier:5596): update-DEBUG: last_launch from /var/log/dpkg.log: 1270722822 (Thu Apr 8 12:33:42 2010)
(update-notifier:5596): update-DEBUG: mtime from /var/log/dpkg.log.1: 1269971797 (Tue Mar 30 19:56:37 2010)
(update-notifier:5596): update-DEBUG: ctime from /var/log/dpkg.log.1: 1270215256 (Fri Apr 2 15:34:16 2010)
(update-notifier:5596): update-DEBUG: last_launch from /var/log/dpkg.log.1: 1270722822 (Thu Apr 8 12:33:42 2010)
(update-notifier:5596): update-DEBUG: mtime from /var/log/dpkg.log.2.gz: 1268049514 (Mon Mar 8 12:58:34 2010)
(update-notifier:5596): update-DEBUG: ctime from /var/log/dpkg.log.2.gz: 1270215256 (Fri Apr 2 15:34:16 2010)
(update-notifier:5596): update-DEBUG: last_launch from /var/log/dpkg.log.2.gz: 1270722822 (Thu Apr 8 12:33:42 2010)
(update-notifier:5596): update-DEBUG: mtime from /var/log/apt/term.log: 1270722823 (Thu Apr 8 12:33:43 2010)
(update-notifier:5596): update-DEBUG: ctime from /var/log/apt/term.log: 1270722823 (Thu Apr 8 12:33:43 2010)
(update-notifier:5596): update-DEBUG: last_launch from /var/log/apt/term.log: 1270722823 (Thu Apr 8 12:33:43 2010)
(update-notifier:5596): update-DEBUG: mtime from /var/log/apt/term.log.1.gz: 1269971797 (Tue Mar 30 19:56:37 2010)
(update-notifier:5596): update-DEBUG: ctime from /var/log/apt/term.log.1.gz: 1270215246 (Fri Apr 2 15:34:06 2010)
(update-notifier:5596): update-DEBUG: last_launch from /var/log/apt/term.log.1.gz: 1270722823 (Thu Apr 8 12:33:43 2010)
(update-notifier:5596): update-DEBUG: mtime from /var/log/apt/term.log.2.gz: 1268049514 (Mon Mar 8 12:58:34 2010)
(update-notifier:5596): update-DEBUG: ctime from /var/log/apt/term.log.2.gz: 1270215246 (Fri Apr 2 15:34:06 2010)
(update-notifier:5596): update-DEBUG: last_launch from /var/log/apt/term.log.2.gz: 1270722823 (Thu Apr 8 12:33:43 2010)
(update-notifier:5596): update-DEBUG: time now 1270723041 (Thu Apr 8 12:37:21 2010
), delta: 218
** (update-notifier:5596): DEBUG: Skipping reboot required