I've had the same problem (the CM15a not recognized; not being able to control anything from within AHP; taking waaay tooo long to d/l macros to CM15a, timers/macros not working, etc.) What I've had to do is unplug the CM15a from the computer and the wall, take out the batteries, and leave the CM15a sitting there for a few hours - sometimes as long as 8 hours. I usually reboot my PC, install any Windows, java, viewers, etc. updates while I'm waiting. Once the time is up, I install the batteries, plug the unit back into the wall, and connect it to the PC again.
Once it's detected and properly recognized, I start AHP, select "Clear Interface Memory", then "Download Timers and Macros".. That's it.
At first, I had to go through this process every other day. As time went by, I've had to do it once a month or even every other month. My take on it is that the CM15a simply get confused and needs a total reset. The way I can tell that it's time to do it again is by looking at the "Activity Monitor" (F2 in AHP.) I have a bunch of X10 sensors, light switches, sockets, filters, signal amplifier, two-way floodlights, and more, which means that the "Activity Monitor" has an entry every few minutes.
If the last notification is over an hour old, it's time to reset the CM15a. Sometimes, I notice that my regularly scheduled security/outside lights don't go on/off as they should. That's another clue. I think you get the point. I would give this a shot if I were you.
In your case, since you're close to other X10 traffic (your neighboors'), it's possible that all of that combined may be throwing your CM15a into that state. good luck!