Thank you all for helping me understand the functionality of CM19A. From your comments it appears that the function of CM15A or the HD11A unit I have been using, which accepts, stores and transmits timer instructions to lamp modules etc is approximated by the CM19A/TM751 combination. One key difference however, is that the CM19A must send a wireless signal to TM751 for transmission to a lamp module while that step is obviously not necessary in the case of CM15A nor HD11A. From what i have been seeing it appears that that wireless data transmission is unreliable (perhaps due to a faulty CM15A) causing my problems. Another difference may be that unlike CM15A or HD11A, CM19A does not store the timer instructions and merely transmits them from AHP to TM751.
I havde an appointment to speak to an X10 level 2 tech on Tuesday at which time I'll try to verify these beliefs. If this is all true, it appears that I would want to replace CM19A with CM15A. I have tried to find CM15A as a stand alone item on the X10 website without success.
Also, I have questions about MyHouseOnline. Must you have your computer on at home in order to access AHP from a remote computer? Further must you install AHP on the remote computer to be able to install the plug in which permits remote access?