Since this thread has come back to life my two cents is this:
I have been a participant on this forum since it began, and a user of X10 control/automation products since 1979 when their "pilot marketing" hit south Florida.
There simply is no "history" of X10 modules "bursting" into flames. IMHO where X10 modules have overheated or went thermo nuclear, there were probably external factors which caused it. Non incandescent bulbs connected to modules that X10 has clearly labelled "Incandescent Bulbs Only" , modules used in wet locations, modules with loads exceeding their stated load maximums, external shorts on the load side of the module, etc. etc. I am regularly amazed at continual abuse of users expecting lamp modules and dimmer wall switches to run ceiling fans, or CFL bulbs, or LED bulbs.
I think one exception is the 500W rating on the WS467 and WS12 switchers. IMHO running 500watts might be OK if the WS467 is mounted in a metal wall box, but when mounted in a plastic box with a big decorative wooden plate over the top, really impedes the switches ability to dissipate heat.