Exactly where is the lid-shut sensor on Thinkpad Edge 14?

[Mugurel]

Greetings!
I have a problem with my Thinkpad Edge 0758-kqg: The sensor that deals with lid's position seems to malfunction.
More exactly, sometimes, usually when the laptop is not perfectly horizontal, although the lid is in the normal (opened) position, the backlight on the LCD closes, and some programs stop working/minimise to desktop, like the lid has been closed. Sometimes this happens when I press some keys in the right part of the keyboard (it's a random thing there is no specific key involved), sometimes it just goes dark. If I tap (more or less) gently in the right part of the laptop, outside the keyboard, it returns to normal.
It returns to normal because in the power management settings I set the Windows to do nothing on lid closure.
I see different threads dealing with disabling that sensor on other Lenovos (http://www.thinkpads.com/forum/viewtopi ... 30&t=89025 is an example, it's more or less the same issue, but in my case it closes by itself). I was wondering if anyone had a similar problem on Thinkpad Edge, and how he solved it.
If no, does anyone know where the sensor can be found on Thinkpad Edge 14 and how I can reach it to disable it?