I have a nice touch light that I had bought some time ago. It works with a simple voltage change logic but recently started switching automatically (better to say unexpectedly). I started googling whether there are some other people having the same problem and I found out it is a well known problem.
Here is one of the useful links :
http://boards.straightdope.com/sdmb/showthread.php?t=551416
I hope you also find it useful.