When you configure the system with dual monitor xinerama, everything works fine exept the notification area, goes crazy when I try to raise or lower the volume for example that flashes across the systray appears on both screens.
I use: ATI Radeon HD 5670, With Ubuntu 11.10 x64 clean, not any strange soft or theme, only ATI driver configured in dual monitor with xinerama.
*Note: Sorry, for my bad english.