Though the original person asking the question implied he's running Ubuntu 8.10 many people, using later versions of Ubuntu might stumble here as well. And this might in fact work with 8.10 too. I dunno, I don't have any 8.10 installations to try it with..
Ok, lets cut to the point. So the cool "new" way of controlling services is to use the
service command. So you can reload configs with the following command:
service postgresql-8.3 reload
naturally you need to have the proper rights so it is most likely required to prepend the command with something like
su -c root like this:
sudo service postgresql-8.3 reload
su -c root 'service postgresql-8.3 reload'
P.S. It is suggested in the Ubuntu documentation that something relating to this new method had been done way back there with the release of 6.10, however if I've understood it correctly it had not been taken into more general use until 9.10.