Comment 8 for bug 1301589

I have the same issue, but may have found the source & potential workaround.

When I use a monolithic site-wide passwd file, indicator-session crashes. When I strip it down to just a local account, everything is fine. After I stop showing the users for quick user switching, it stops crashing!

Possible workaround: Run the command below as the affected user.
dconf write /apps/indicator-session/user-show-menu false

I've actually applied this as a manditory setting on a system-wide level. Apply the attached tarball, then run 'sudo dconf update'