I just purchased a 15" rMBP, 2.3 GHz i7 and trying to hook up to 2 external monitors. one a Dell U2713 and the other Dell U2711. 1. I'm trying to run a powerpoint slide show on one external and have Skype video call on the other. The powerpoint runs on external and the rMBP display, but the 2nd external is blank. How do I fix this? 2. In the display settings, it's not showing the full 2560 x1440 resolution. Anyone has any idea how to fix this?