User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.1b99) Gecko/20090605 Firefox/3.5b99 Build Identifier: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.1b99) Gecko/20090605 Firefox/3.5b99 I did a fresh install of Ubuntu 9.04 AMD64, installing ia32-libs to be able to run Firefox. Firefox can't do DNS lookups. I can only load sites by IP address. This is with a fresh profile in a fresh home directory. Reproducible: Always Steps to Reproduce: 1. Install fresh Ubuntu 9.04 AMD64 2. apt-get install ia32-libs to run the 32-bit binary of Firefox 3.5b99 en-US from the Mozilla site. 3. downloads and extract the tarball from the Mozilla site, the path I used was /home/username/.bin/firefox 4. attempt to load any web page involving a DNS lookup Actual Results: pages should load when the DNS-based URL is typed (eg http://www.google.com/) Expected Results: A "server not found" error is displayed. Doing a tcpdump on my gateway, I get the following: # tcpdump -ni vr0 src host 192.168.0.22 and port 53 tcpdump: listening on vr0, link-type EN10MB 21:05:39.645653 192.168.0.22.40235 > 192.168.0.1.53: 45936+ A? ftp.mozilla.org. (33) (DF) The query for "ftp.mozilla.org" was from when I used wget to download the Firefox 3.5b99 tarball, however this was the only DNS packet seen from the host while I was reproducing the bug. I found two workarounds: The first is to set network.dns.disableIPv6=true. This network does not have any v6 connectivity. The second is to set offline mode, try to load a page, and then set it online again. The second workaround appears to alter some state such that it works from then on even with subsequent sessions. I have another Ubuntu 9.04 AMD64 machine running the 32-bit Mozilla-provided binaries, and recently updated to 3.5b99 there. I have not encountered this problem on that machine.