Macbook sleep sensor broken

Hi,

My Macbook 13" (early 2011) all of a sudden won't go into sleep mode.

It was working just fine but yesterday when I closed the lid it didn't go to sleep mode and therefor kept the screen on.

I've been wandering around on the internet and some say it's the reed switch or the hall effect sensor...Tried several suggestions from deleting the power management plist file, to passing a magnet over the side of screen and over the side of the keyboard, but none of them worked.

Is there anyone with the same problem?

And has anybody found the solution for this?

Thanks