I have an Acer X138H 18.5" display with a 1366x768 resolution. When I plug it into my 2010 13" MBP via an Apple genuine (from Apple store) MDP-VGA adapter, it defaults to 1360x768 display resolution on the Acer display. When I go into system preferences to change the resolution to 1366x768, there is an option to do so. Not that it is a big issue that I am using 6x768 pixels, but I am wondering why it does this. I have reset the SMC and PRAM, and it has not resolved my issue. I have the Acer display hooked up to a KVM switch. I hook up my MBP and headless MacBook (see sig) to it. The MBP will not show the full 1366x768 resolution (as noted above), but the headless MacBook will display the full resolution. It has an Intel GMA 950 GPU. My (non-headless) 2007 MacBook with an Intel GMA x3100 GPU will also display the full 1366x768 resolution. It seems odd that my 320M will not display 1366x768 video, as the 11.6" MBA (also with 320M) has an 1366x768 display built-in. Note: the connection between all of my MacBooks/MBPs is between the KVM switch and an Apple-genuine Mini-DVI/Mini Displayport adapter.