Simple way to debug gnome hang during startup?

["Walter Prins" <wprins gmail com>]

Hello,

I'm trying to help someone with a Gnome startup issue, they've been having after an OS upgrade.  I've searched the gnome mailing list archives and haven't really found anything specific about how to go about debugging a situation where the login process hangs partway (as opposed to a crashing application where you can try to obtain a stacktrace ala here.)   Things I've suggested:
1.) Move/Remove .gnome* .gconf* .metacity*    [Made no difference]
2.) Check ~/.xsession-errors [Waiting for feedback]
3.) Check if there's firewall/net filtering software running [Waiting for feedback]

The login proceeds to displaying the desktop wallpaper apparently, but no further.  An altenative window manager (fluxbox) works fine, so it's ostensibly not video drivers or somesuch.

I'm wanting to know whether there's a fairly simple way to enable debugging/logging somewhere so as to be able to see how far the startup process gets/where the problem might be.  

Many thanks for any suggestions, much appreciated!

Walter