Here's my setup: I have a (late 2008) unibody Macbook Pro connected to an external monitor via mini-displayport to HDMI. The MBP is closed and the external monitor is my only display. I have a USB hub connected to the MBP which is connected to a mouse, keyboard, external HDD, etc. My problem is, the computer won't go to sleep unless I manually select the option from the menu. In the Energy Saver settings, the monitor and computer are both set to go to sleep at 15 and 20 minutes, respectively, and the monitor goes to sleep just fine. The computer never does, as indicated by the solid white indicator light on the front of the MBP and the fact that it stays warm after not being used for hours. I have not added any applications since I started using the monitor (just after this Christmas), and the difference compared to my old setup are the USB hub (keyboard is only new device connected by USB) and the mini-displayport cable. Those are pretty much all of the details I can think of. Any ideas as to why my laptop won't sleep on its own? On a somewhat related note, my USB wireless non-Apple mouse, which I have been using for months, sporadically freezes completely for a few seconds at a time only when I am using my MBP closed, with or without a USB hub in between. Any thoughts on that as well?