Infamous Checkered Screen

Jolly Walia mightykernel "at"
Tue Mar 30 19:33:00 2004

First time, so here it goes.
I have installed the vncserver on a hpux 10.20 workstation with the following in my xstartup file:
[ -r $xsession ] && exec $xsession
# Fall back if the script wasn't readable or the exec failed
xrdb $HOME/.Xresources
xsetroot -solid grey
xterm -geometry 1024x768 -ls -title "$VNCDESKTOP Desktop" &
twm &
When I use realvnc viewer on a win xp laptop, I get a prompt for the password, I enter it, I see a screen which disappears within half a second.  If I try to login again, the server isn't found.  I have to restart the vncserver in order to get back to where I started from.  On the other hand, if I use tightvnc viewer, I login, screen comes up, I see the blue hp logo, but eventually it becomes the checkered grey/blackish screen.  My laptop resolution is set to 1024x768.  Also, I have tried to run the xstartup script without "twm &", but to no resolution.
Any help would be greatly appreciated, thank you.