[ubuntu] Virtual Box Seamless Mode not working correctly.

So I'm running Ubuntu Studio 12.04 as my main operating system, and Windows 7 as virtual machine using Virtual Box. I installed Guest Additions to the Windows 7 VM. But when I put the Widnows 7 VM in to Seamless mode, the Windows 7 desktop background and icons disappear showing my Ubuntu desktop and all it's icons. The even more screwed up thing is the Windows 7 task bar appears, but not the actual desktop.

Any ideas?

Thanks