Sometimes a client marks itself as restart immediately (via xsmp or .desktop) but can't be restarted for some reason.  See bug 634761 for example.

We probably shouldn't keep trying forever.  The question is what should we do.

Maybe something like this.

 * (can we tell this?) If there is no way to display a message to the user at all then the session should exit and signal to the "display manager" or "session session-manager" that it failed to start.  Perhaps exit code is enough here unless we need to provide a reason.  Though I'm skeptical that a reason is going to be interesting for anyone but an admin.  So perhaps reporting something to the log is enough here.
 * If the program is a required component and it isn't running (needs to be checked independent of the restarting since it can be started out of band) then we should indicate to the user that a fatal problem has occurred and cannot continue.  And offer to logout after presenting an apology.
 * If the program is an app and it was started implicitly by the session (not from direct user interaction) and it isn't running (needs to be checked independent of the restarting since it can be started out of band) we can present a non-modal notification that the app failed to start.
 * If the program is an app that was launched explicitly by the user then we should:
  - display a system modal dialog apology IFF it was still "focused"
  - display a notification apology if the user task switched before the app started (basically same as implicit scenario above)

Apology screen would ideally have one of the following modes:
 * Crash
 * Misbehavior
 * Misconfiguration
 * Failure 

See http://live.gnome.org/GnomeShell/Design/Whiteboards/ProblemReporting for some more discussion.