No window appears, no error message is printed, and the process terminates immediately. 

Deleting ~/.conkeror.mozdev.org/ does not fix the problem.

To clarify, when you say "latest", you mean from git master?

Yes, from git master.

Can you identify for me as specifically as possible (with url if possible) the version of xulrunner that
is giving this problem?  Was it built by you or was it a binary package?

I'm using the binary package in Arch Linux: http://www.archlinux.org/packages/extra/x86_64/xulrunner/.

I can confirm that with xulrunner 2.0 from arch linux (x86_64), conkeror (latest git master) fails to 
start. 

http://www.archlinux.org/packages/extra/x86_64/xulrunner/

Unfortunately, the packaging script for building the binary has not been updated on the servers yet, so I 
cannot provide a link to the source used to build the package.

Try the x86_64 build from here:

http://releases.mozilla.org/pub/mozilla.org/xulrunner/releases/2.0rc1/runtimes/

You'll have to do manual GRE registration to put a necessary file in your ~/.gre.d/

$ cd xulrunner
$ ./xulrunner --register-user

You might also temporarily remove the file /etc/gre.d/2.0.system.conf to ensure that the run-conkeror
script (which is in conkeror's contrib/ dir) will definitely use the right version.

Also could not start conkeror with xulrunner 2.0rc1.

http://releases.mozilla.org/pub/mozilla.org/xulrunner/releases/2.0rc1/runtimes/xulrunner-2.0.en-US.linux-
x86_64.tar.bz2

I uninstalled the the arch linux xulrunner and followed the installation steps at 
http://conkeror.org/InstallationUnix , except that I used the link above to download conkeror.

I also reported this bug on the Arch Linux tracker (I am using the conkeror-git binary package) and the
problem seems to have been solved: 

https://bugs.archlinux.org/task/23393