X session ends within seconds of login

[John Hupp]

I'm trying to get Linux Thin Terminal Server working under Saucy i386, 
and I find that on a client machine the X session ends within seconds 
and returns me to the LDM login screen.

LDM.log merely notes something like "x session started" and then 
immediately follows with "x session ended." I don't see anything unusual 
in the xsession-errors log for that user.

It doesn't matter which user account I log in with.

I have tried a couple different clients with different video cards, one 
an old Intel and the other a current Radeon, both with plenty of RAM.

The problem only appears with Lubuntu Saucy.  I have not seen it with 
Ubuntu Saucy.

The problem did not appear under Lubuntu Raring.

Suggestions?