All communication with Launchpad is conducted using MIDI note-on, note-off, and controller change messages. Therefore if any MIDI data is being sent to the Launchpad, the pads on the unit which correspond to the MIDI data being sent will cause the LEDs to flash.
The way to prevent this from happening is to ensure that none of your MIDI channels are sending MIDI information to the Launchpad. The images below show a comparison between two MIDI tracks in Live in which one is set up to send MIDI to the Launchpad, and the other is set up so that MIDI data is NOT sent to the Launchpad. The annotated track shows the settings needed in order to prevent the aforementioned problem from occurring.
If you deliberately want to send MIDI data to the Launchpad for LED feedback, and need to know how to control this problem in more depth, please click here for further reference.