Hard to figure out what you are asking.
If I understand: you have three lights all addressed to A1. What modules control these lights?
You have one wall switch addressed to A2.
Suddenly the three A1 lights quit working, but the transceiver still clicks. That at least indicated the transceiver is receiving the key chain remotes signal RF, BUT the PLC (power line control, or power line carrier) signal the transceiver puts on your power lines is no longer getting through the the three modules you are using to control the A1 lights.
IF the A1 lights are still plugged in to the same outlets where they originally worked AND the transceiver is still in the same outlet where it originally worked, a sudden failure would indicate an electrical noise problem. CFL bulbs are one source for this interfering noise. Switching power like used in computers "power bricks" flat screen TVs, etc are an outher source. Search this forum for "noise"
IF the three lights OR the transceiver have been moved from the original outlets where they originally worked, you may have a phase coupling issue. Search this forum for "Coupling" "Phase", "phase coupling", and "repeaters".
X10 is an inexpensive method of remote control, but there are a number of things that can make it difficult to get the X10 signal throughout the house to all the modules you want to control. It is not difficult to fix, but just takes some effort to identify which set of problems you may be having..
Typically this indicates a noise problem. and the