...The CM15A stopped sending any type of on or bright command. Interactively through the latest version of Active Home Pro or via a timer.
It sounds like the common "SoftStart" problem.
I'm going to guess that:
1) Prior to upgrading your AHP to the latest version (presumably 3.318), you had a version that was older than version 3.302, and
2) The lamp modules you are using are older than around 2008.
Here's the background:
Around 2008, X10 changed the design of the lamp modules (and dimming wall switches) to incorporate the newer, more precise "Extended Dim" commands. Unfortunately, they didn't bother changing the model numbers of these newer modules. The problem is that while these newer modules still responded to the same "percent dim" commands as the prior design, the older modules (prior to the redesign) did not understand the newer commands.
In January 2011, AHP was updated to version 3.302, which added support for these SoftStart modules. Since they carried the same model number as the newer ones, and since all modules being sold by them were at that point the newer ones, they made the default behavior in AHP be to use the Extended Dim commands.
There is a simple solution (of course, not well-documented by X10).
1. In AHP, right-click on the modules that aren't working, and click on "Edit Module".
2. From the "Type of Module" drop-down, choose "Old Lamps - no Soft Start."
3. From the "Module" drop-down, choose the correct module type.
Click OK, save your changes, re-download to the CM15A, and test it again.
If this doesn't work, or if my guesses (#1 and #2 above) are not correct, please let me know.