Comment 29 for bug 545134

I can confirm that this is still a problem in 12.04. Go to Network Settings -> Network Proxy and then enter my settings... apt doesn't pick up the proxy, and the Software Center doesn't work. Have to manually enter settings in /etc/apt/apt.conf.d to get any joy (works fine after that). Firefox and Chromium both appear to respect the system wide proxy -- kinda ironic that such a core part of Ubuntu doesn't.