Docking a MacBook Air

I have to tell you that I used to "dock" my MBA (Lion OS, 13'' mid 2011) by simply connecting it to the usb-hub with all the peripherals (keyboard, mouse, etc) a screen (through the thunderbolt port) and the power. I was really surprised that it worked smoothly the first time I connected it all, exactly in the way I intended (it never does with a pc). When the laptop was still in the stand-by mode and was closed, it could be "docked" and woken up by the external keyboard, getting picture only on external screen (exactly as i preferred). This setup worked well for months until now. The problem is really that MBA doesn't wake up by the external keyboard. Furthermore, when it is awake and the external screen is connected, i'm not able to close the MBA because it goes back to the stand-by mode. This issue gets pretty irritating. Anyone has an idea what has gone wrong and how to fix it? Thanks in advance!