I'm having issues when I reboot my Ubuntu Desktop system, then try to VNC to it from another system, the Ubuntu desktop keeps poping up a login screen similar to the authentication that a user needs to allow for the vnc session to start.

Once I login at least once, then any subsequent VNC sessions will no longer do this popup and simply allow the vnc session to complet.

This is somekind of security on the Ubuntu side, but none of my other systems (centos5) request this first time password everytime the system is rebooted.

Not sure if you understand ....

Anyway to stop this first password request on the host Desktop?

This is ver anoying as someone has to physically be at the Desktop and enter the password in order for my session to continue, but my problem is that this is a headless system....