I have the same errors as others. After hours of searching and experimenting, I found the solution.
I have a Dell Inspiron mini 10 netbook running window 7 with Intel Poulsbo graphics chip, which is pretty useless piece of hardward otherwise. Nevertheless I found it to be a good use for xbmc.
In my case, the reason upon starting xbmc and crashed with "error Unable to create GUI", is because my DirectX feature (directDraw, Direct3D) acceleration not enabled. To check that, run "dxdiag.exe" on your window OS and under the Window tab, it should list the DirectX features.
To enable DirectX Acceleration feature, I download Intel Graphic Media Accelerator driver. After downloading, simply run the "Setup.exe" and it will take care the rest.
https://downloadcenter.intel.com/Detail_...ldID=18470
After that my xbmc no longer plagued by the "Unable to create GUI. Exiting" error. Good luck to you.