Its a fresh install of Suse 11.4
I connect to domain.com:5901 and it takes me to the logon screen. As soon as I put in the usrname and pass the window closes.
I tested with a bad username and pass and it just said the bad username etc, I wanted to rule out the actual logon action.

Any ideas ? I am totally lost here :|

my suggestion.

1) kill all the vncserver process as root
2) login ssh as user or su - user then proceed as below example

then make connection with the port given

if NOT work then please paste here the contain of $user .vnc/xstartup

if work then you can start use ssh vnc tunneling for more security in mind

cheers

Perhaps the problem is vncserver shows the login program (kdm/gdm/xdm/whatever) and when you type user and password, X stops and starts again a session for the supplied user.
You could try x11vnc program, something like -auth guess is to look at standard places for the Xauth file, some login managers change the name of the file so it may not work 100%
-display :0 is self-explanatory
-rfbport allows custom port for the vnc connection
-rfbversion 3.6 is to enable filetransfer if you connect with ultravnc client
-forever is preventing VNC server shutdown after client disconnect, the default is shut down x11vnc after client disconnect
-passwd is, well, password