Controller floodlight?

controller floodlight?
Originally uploaded by modernemama

I think I may have solved the mystery lighting issues we have been having in the den. Solved them, but not begun to understand them.
This floodlight is situated on the front drive, and I actually didn't discover it until late last year when I did a lot of pruning on the north edge of the property. When we moved in three years ago there were huge raggedy old junipers on the edges of the driveways and buried in these were lights that had been hit (probably by the snow plough). They had once been crescent shaped modern post lights but by the time we dug them out they were busted and rusted and there was nothing left to salvage.
I had an electrician put in new lights at the end of the drive and the only thing that's slightly irritated me ever since is that they aren't automatic. Gradually as I took out overgrown plants, weeds and tons of ivy, I discovered other light sources scattered throughout the flower beds and I began to put uplighters and floodlights on these. They are all connected to the same switch that the drive lights are on.
On Thursday I was outside tidying up when I noticed that the lightbulb on one of the floodlights had been smashed. So I replaced it. Since then we have had no gremlins in the den lights.
I can only surmise that at one time this outdoor lighting system worked on a timer and motion sensor system that was also connected to the den lights. For some reason when the lightbulb was gone (and only shards of the bulb remained) the sensor kicked in. This doesn't make very much sense to me but why else would the lights in the den have given up their independent ways?
I wish the original owner had thought to post a cheat sheet in the control panel of all the x10 lights when he installed them. Or just a guide to which switches control which lights. Anything would have helped. Three years and three months in the house and we still have figured out the electrics. Heigh ho.