I've had the same issue with the apt acquire::http::proxy being set to 'false' preventing it from working with apt-proxy. With the setting as is, apt sends a 'GET http://hostname:portnum/ubuntu/etc' request instead of just 'GET /ubuntu/etc', which causes apt-proxy to (probably wrongfully) barf.
-- apt cant work with disable proxy https://launchpad.net/bugs/47044 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
