My Bluetooth turns itself off

I've been using Bluetooth to send .mp3 files from my Macbook (running 10.6.8 Snow Leopard) to my Android phone for a while now, and normally it works very well!

However, tonight my Bluetooth just isn't cooperating. When I clicked on the little icon on the top bar and hit "Turn on Bluetooth", nothing happened. And then, when I opened up the Preferences section for Bluetooth and clicked on the checkbox labelled "On" in order to tick it, the box literally turned itself back off half a second later.

What the heck is up with this?