Some things that could help diagnose your problem:
What is your installation source? Net install, DVD Beta2 install, Snapshot install?
What video card are you using? Nvidia, ATI, Intel, VIA?
What model of video card?
How are you connecting to your display? Composite, SVIDEO, VGA, DVI, HDMI?
How long have you waited after the AVWizard? (It could take more than 20 mins to build the orbiter before showing the Setup wizard.)