Alright, here we go:
From your post, it sounds like you can use the CM15A to control both modules, but you can no longer use the SS13A to control them. That rules out most powerline noise issues. It also rules out SoftStart/Non-SoftStart issues. That leads us to an RF signal issue, most likely.
In order to control the lights from the SS13A, you need a transceiver to pick up the wireless RF signal, and pass it to the Powerline (as a PLC signal), so it can get to the modules.
1. Before you put in the CM15A, how were you getting the signals from the SS13A to the LM465 and WS467? You were probably using either a TM751 or an RR501 (or an equivalent with a different model number). Did you remove that when you plugged in the CM15A? Is the CM15A plugged into the same outlet where the TM751 or RR501 had been?
2. Have you done any programming of timers and/or macros in the CM15A?
3. What HouseCode / UnitCode do you have the WS467 set to? (you indicated the LM465 was on A1).
There are a few things I can see that can cause this:
A. You removed the TM751 or RR501 that was picking up the RF signals and sending them to the Powerline. The CM15A has an RF transceiver in it, but you need to make sure it is set to transceive the correct HouseCodes. If you didn't set the CM15A to transceive those signals, they'll just get lost in "thin air".
B. You DID set the CM15A to transceive those signals, but the CM15A's limited RF reception range is shorter than that of the TM571 or RR501, so it is too far away from the SS13A to hear the RF signal. There are a number of fixes for that, and we can help you with that if it is the case.
As for the second part - the lights being on when they shouldn't be, here are my thoughts:
C. You created some timers and/or macros that address either device, and those are being triggered at night. The CM15A doesn't require the PC to be on, for at least some functions. You can download timers and (some) macros into it, and they will run even if the PC is turned off or disconnected from the CM15A.
If you leave the PC turned on and connected to the CM15A, AHP will record a log of the activity it sees (and sends) on the powerline and RF, and you can view that in the Activity Monitor. That might give you some more clues as to what is happening.
D. You created some macros or timers, and then deleted them. You didn't, however, clear the trash in AHP, and/or download the updated program to the CM15A. Deleted macros and timers have been known to continue to run from the trash.
E. You might have a neighbor who also has X10, and you are both using the same HouseCode. Again, this isn't all that likely, since the problem only started when you added the CM15A. However, the Activity Log should give you some clues about this, too.
F. There is other powerline noise, which the modules are picking up on, and turn on by themselves. I've had this problem before, and I ended up replacing the modules. However, since this wasn't happening before you installed the CM15A, I would consider this theory a real long shot.
The more information you can provide us, the easier it will be for us to work through this, and help you.