Just an idea:
... do i get you right, that switching to :0 and back to :1 after calling X -ac :1 & doing nothing else inbetween kills the xserver on :1 ? you can check that with ps ax | grep X
if this is the case then there might be a problem with your general graphics setup. maybe you can find some info in /var/log/Xorg.1.log ...
To check this maybe you can try the Xnest X server. This one starts an X11 server inside the existing (correctly running) server, see http://www.xfree86.org/4.2.0/Xnest.1.html Start Xnest instead of your full featured :1 server and redirect your remote X11 requests to that X11 server With this you can check if it is some hardware related problem of your local full featured X11 server or some software related authentication problem... Greetings, Dirk.