I can confirm this bug too. It started when I dist-upgraded to dapper from breezy. Since then... I have no update-notifications anymore, except when I manually do sudo apt-get update. THen it notifies and recognizes the available updates. But it does not do that by itself. I am jalous on the fresh 7.04 install on my wifes pc for this :-) This notifies correctly.
I can confirm this bug too. It started when I dist-upgraded to dapper from breezy. Since then... I have no update- notifications anymore, except when I manually do sudo apt-get update. THen it notifies and recognizes the available updates. But it does not do that by itself. I am jalous on the fresh 7.04 install on my wifes pc for this :-) This notifies correctly.