Comment 3 for bug 111636

Also, remember that Feisty moves us into line with Debian and defaults to apache 2.2... Here are some notes that I ran into when upgrading from apache 2.0 -> apache 2.2 using the Debian package, (which is almost identical to the Ubuntu packages):
http://speeves.erikin.com/2007/01/debian-apache-20-apache-22-upgrade.html

They might touch on some issues that you may be having... Here are some more links with notes on the upgrade:
http://www.debian-administration.org/users/lee/weblog/31