Seamless mode not displaying desktop

[Irrational]

I am running VirtualBox v4.2.4 on a Windows 7 Home Premium 64-bit host. The guest OS is Windows 8 Proffesional. I installed the newest Guest Additions but when i switch to seamless mode I ca only see active apps(windows explorer, internet explorer etc..but when i close them and go to desktop on Win 8, instead of seeing Windows 8 Desktop i see Windows 7 Desktop and Windows 8 taskbar.

[mpack]

So far, that seems to be an adequate description of seamless mode doing what it's supposed to. What is your question?

[Irrational]

]Yea....I kinda mixed up fullscreen and seamless...sorry But now another problem showed up...When i switch to fullscreen it blacks out ..except some items on the start menu(items that update themselves) and the ones i hover over ...

[mpack]

What size of display is it when fullscreen?
Have you installed the Guest Additions?
How much Video RAM did you allocate?

[Irrational]

1366x768(fullscreen)
Yes
256 MB