Go into your main fubar options (rightclick action bar/click fubar at top left side of box that opens up).
There you should have an option for 'Thickness', I think the default is five. Setting this to 3 sorted it for me (after trying a couple of settings).
Only does it now when I log a toon on for about 2 seconds, then it is plain sailing.
P.S. love the site and the plugin. Keep up the good work people.
Every time i initiate combat, my screen shifts back to its original position and my buttons,bags, etc.. get partially covered up by fubar. Once combat ends the screen shifts to be below and above fubar, as it should be. Any ideas on whats causing this. Only started happening since i downloaded and started using WoWAceUpdater.