I'm on Ubuntu 9.04. I've updated Firefox with ubuntuzilla. Now Firefox forks only via proxy. How can I fix this?
I'm guessing from your question that before the update you were able to access the internet without a proxy.
Instead of using Ubuntuzilla, I would use the mozilla team's official repository, and install the latest stable firefox from there. The repository is located at https://launchpad.net/~mozillateam/+archive/firefox-stable and it explains how you can add it to your software sources, you need to click on the technical details drop-down.
Once you've added the new repository (and maybe removed ubuntuzilla's repository) you may need to reinstall firefox, or even purge then install again. On the other hand, it looks like ubuntuzilla names their packages differently, so just removing the package firefox-mozilla-build should clear it.
However, this may remove all your settings / bookmarks as well, so before removing anything be sure you're clear on what you will lose. Your user settings are stored in a folder ~/.mozilla so I would make a backup of that before you start removing things. I still cannot guarantee that there isn't anything stored elsewhere that you may lose though.
I use the packages from the mozilla team's firefox-stable repository and I've not had any problems, it may just be the ubuntuzilla's unofficial packages that have the problems in them.
This is just a guess, it may not solve your problems, which may not be to do with firefox and something else instead, but I'd try this first as it was the update that broke it.