Instructions
Unplug the wireless guitar receiver and plug it back into a USB port on the front of your PlayStation 3. The receiver lets your controller communicate with your PS3. The receiver is powered off the electricity from your console. Unplugging the receiver and plugging it back in will reset it, which should allow you to connect your guitar controller again without any issues.
Press the "Connect" buttons on both the guitar controller and the wireless receiver. A miscommunication between the two devices could cause the connection signal to be lost without you becoming aware. As a result, your controller would suddenly stop working. Press both "Connect" buttons in an attempt to pair the two devices together and then attempt to use your guitar controller again.
Disconnect all other controllers from your PlayStation 3. Like the "Guitar Hero" controller, all controllers that connect to the PS3 are wireless. The PlayStation 3 has a limited number of wireless devices it can connect with at any time. If you have multiple Dual Shock 3 controllers connected to your PS3 in addition to another guitar shaped controller and a wireless drum set, this could fill up all available slots. Disconnect all other controllers and attempt to use your guitar and wireless receiver again.