My ps3 controller isnot connecting!

I am trying to connect my wireless ps3 controller via ps button. I press the PS button and all four LED lights start to flash, like it should, but it stays like that, and then it seems like it times out and shuts off. I have another controller that works fine. Please help! The controller is hooked up with a usb cable so it should be fine. Right?

that happened to me once, i let the controller time out and shut off, then i turned off the ps3 from the back switch , then turned it back on connected to controller to the ps3 with an usb cable and turned it via ps button, once it turned on i unplugged the controller from the usb port and that was that if i remember correctly

edit: btw first post? welcome then :D