Okay. first of all, make sure the modules you have really are SoftStart.
The simple test is to use a remote (either a PalmPad, or a plug-in tabletop controller) to turn the lamp on. You can also use the "local control" by turning the switch on the lamp itself off, then back on. Any of those should turn the lamp on. Watch it as it turns on. If it "ramps up" over a second or two to full brightness, then it is SoftStart. If it goes right to full brightness immediately, then it is NOT SoftStart.
Once you have confirmed the module type, you need to see if you have signal issues with your X10 setup.
Define the lamp as an Appliance module first (you'll only have on and off, no dimming). Make sure you can control it directly from the CM15A with the software (turn it on, make sure it comes on, turn it off, make sure it goes off). Once you have confirmed that works, THEN re-define it as a Lamp module (from the "Lamps" category for SoftStart, or from the "Old Lamps - no SoftStart" category for non-softstart), and see how it goes.