What actually happens at logout?

[Rupert Swarbrick <rupert swarbrick lineone net>]

I've been upgrading (and probably breaking...) various libraries on a 
Slackware 9.1 system.
Unfortunately, the logout button in gnome now doesn't appear to do 
anything and then after some timeout (1 minute, possibly), exits pretty 
ungracefully. I'm sure that this is a kill, as logging back in, lots of 
windows come up from ~5 logins ago.

What I want to know is whether errors get logged somewhere, so that I 
can see how I've broken things, or better still, what command is run, so 
I can log them myself.

Thanks in advance,

Rupert