Hi Jeff,
I wasn't around yet when TomJ was writing about his MS10a problems. I hope that he and X10 were able to resolve them. At first my two new MS10a modules did not seem to work. I would set them on the shelf, try to set them off, and at first they would not go off. Rereading the manual, I discovered why: they are supposed to wait 45 seconds (I think that was the number) after motion detection before detecting and sending again. My putting them up on the shelf caused one motion detection that I did not think about, so of course they would not detect again for a time. After I realized this, I retested properly, and they worked fine. I do not suppose that this was TomJ's problem; I cannot comment there. All I can say is that mine have detected motion properly so far, and have given no false alarms. I hope this helps. Best wishes to you.