Laptop resumes instantly from going into suspend [Toshiba Satellite L755] [12.04 beta 2 LTS]

What happens is, when I go to shut my lid on my laptop, the computer goes into suspend, as it would normally, for 1 second. Then, the computer immediately wakes up, however, the screen is still black, it's only when I shake the mouse that the login screen appears. What's going on?

Close the lid, laptop goes into suspend for a second, then immediately, the lights on the laptop go from saying its suspending to saying its awake. The laptop should suspend and only resume when I open the lid again, but it just resumes automatically after 2 seconds.

The laptop is a Toshiba Satellite L755.
Running Ubuntu 12.04 LTS Beta 2, recently upgraded.