You may have several issues to deal with. One is the use of CFLs and LED lights. Some CFLs can generate a lot of noise in the X10 frequency band, and interfere with X10 communication. Some 120V LED lights are also powerful noise generators. While the noise level from a single CFL should be relatively constant, noise from several CFLs running at slightly different frequencies can sum together, and almost mimic real X10 commands. I have seen the ESM1 report such noise as valid X10 commands, and that might be a source of some of your unwanted commands.
If any of your CFL or LED lights are producing noise in the X10 frequency range, they can be isolated with filters. The X10 Pro XPPF can be used for plug-in devices, and the small Leviton 6287 wired in-line for ceiling fixtures.
Another issue is the use of a large number of motion sensors. As already reported, the TM751 is not a polite transceiver, and will transmit whenever it receives a RF command. It can step on another X10 transmission if one is already in process. If some of those motion sensors are in high-traffic areas, powerline collisions may be a problem. Usually a powerline collision results in the loss of both commands, but it is also possible for a collision to result in an unwanted command.
It has been reported here that the A housecode should be avoided. It is often used for a simple system, and someone sharing the same utility transformer may be sending unwanted commands to your system. Also some battery powered X10 devices default to the A housecode when the batteries are failing, which can be another source of unwanted commands on that housecode.
If you have not already done so, you might want to read some of the troubleshooting series I wrote:
http://jvde.us/x10_troubleshooting.htmJeff