Maggie,
Assuming you already checked trivial things like the background color settings of the EPrime objects, and assuming that the laptop normally displays bright screen filling content properly, you could try to change the resolution of the EPrime Display device. Ideally, the resolution should match the native display resolution of the laptop. EP2 has a new option for this:
http://www.youtube.com/watch?v=LqC011A2g-w. However, you might have to fix the layout of the EPrime objects after changing the resolution...
Best,
Paul