Gnome green screen of death

[leeoliveshackelford at surewest.net]

Good afternoon, dear FreeBSD enthusiast.  I have installed X11 and Gnome on my computer equipped with FreeBSD 9.1. The X11 
and Gnome packages were taken from the d.v.d.-r.o.m. that 
contained the operating system.  The computer is an H.P. Z220 
with an Intel Xeon quad-core processor.  I do not want Gnome 
to start automatically on bootup.  I wish to call it from the 
command line on the local console.  When I have finished 
working with Gnome, I expect the operating system to return me 
to console session from which Gnome was called.  I have 
started Gnome with the command "exec gdm-session".  I do not 
know if the "exec" keyword is necessary, but it worked.  When I 
am finished working with Gnome, I click on the logoff (or 
logout?) button.  The screen turns solid green with none of 
icons, characters, image, or splash.  The computer does not 
respond to the keyboard.  When I cut the power to the computer, 
and then reboot, I receive a sequence of messages complaining 
that ada0s3a, ada0s3d, and so on, are corrupt, and that I must 
run fdsk.  What am I doing wrong here?  The following error messages, which are shown only partially because they flash quickly on the screen, appear before Gnome starts:  

a)  Authority server root file does not exist
b)  .../serverauth.1119doc.... does not exist
c)  X.authority does not exist
d)  ** (gnome-session:1121):  WARNING **: Cannot open display:

On reboot, 
e)  The file entitled root/.xsession-errors contains 368 lines, including the following:
e1)  DEBUG:GsmAutostartAppp This program is not intended to be run as root
e2)  gnome-session: Fatal IO error 35 (Resource temporarily unavailable) on X server :0.
e3)  Window manager warning fatal IO error 35 (resource temporarily unavailable) on display ':0'.

Any and all comments and suggestions will be appreciated.  Sincerely, Newby Lee