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In the post I wrote a few months ago on picking the right lighting occupancy sensor I thought the old Leviton sensor I was using had gone bad when I wrote the following:

And this worked well and good up until October 2010 (it was 2.5 years old) when the sensor started acting up.  As you can see in the picture on the right, the sensor has three modes: Off/Auto/On.  Off and On work just like a standard light switch would.  Auto mode is where the sensor controls the lights.  While in “Auto” mode, when nobody was in the kitchen and the lights were off, they would start flickering like strobe lights.  Or the lights would be on and they would buzz and only come on half the normal brightness.  Or they just wouldn’t come on at all.  If the mode was turned to “ON” the lights would look fine and work perfectly, so I determined either the sensor had gone bad…..or we had ghosts.

Well, it turns out the sensor hadn't gone bad...and we didn't have ghosts.  

After installing the new Legrand occupancy sensor I discovered a feature that wasn't too popular in my household:

But there is a downfall to this new sensor!  You can’t set it so the lights will stay in the “On” mode.

So if we were in the dining room working or eating and we wanted a little extra light, we couldn't put the kitchen lights in manual mode so they would stay on.  I was doing some research on occupancy sensors when I discovered this comment on the review of the Leviton occupancy sensor on Amazon that I had previously removed:

(2) Flickering fluorescents - With the widespread conversion to fluorescent lighting, there is a new problem. The small screw-in spiral bulbs that replace incandescent lights have electronic "ballasts", which are totally different from those on the long fluorescent tubes. This motion-sensing light switch does not go completely OFF when there is no motion. A sensitive VOM will measure about 30+ volts on the hot line. However, there is little current available. The 30+ volts is enough to trigger the ballast on the spiral fluorescents, and it tries to light the lamp, however there is not enough current available and the light tries to go on, drains the minimal charge on the line, and then goes out. This repeats and you get a flicker. ---- You can solve this by replacing one of your lights with an incandescent lamp. This will constantly drain the charge trickle through the switch and prevent the voltage building up to trigger the ballast. I have used 45W and 60W bulbs, and both work. They just go in parallel with your spiral fluorescents. And you should no longer have any flicker.

I thought back to the time when I started having problems with the Leviton lighting sensor and I remembered that out of the 10 spots for recessed light bulbs, I had left 2 incandescent lights in while I replaced 8 with CFLs.  A few days before I started having problems with the sensor I had finally changed the incandescents to CFLs!

So I took out the new occupancy sensor and put back in the Leviton after putting an incandescent light back in the circuit and....WA LA!  Everything works great.

Bottom Line: If you are using an occupancy sensor, make sure it is compatible with CFLs.  If not, use an incandescent in the circuit!