Precision M4800 Power Switch does not work

I have a real stumper.  The power button does not function.  Will not turn on the laptop. I set the bios to power on with A/C, so I can get it to power on by unplugging and replugging the power cord.    When Window has power switch set  to sleep or to shut down -- it does not.  Holding the power switch down will not shutdown the laptop. 

I installed the latest bios from the support pages.  I replaced the CMOS battery.  I replaced the power switch. While I had it opened up I checked for loose connections, debris, dirt, etc.   At least to the point I had access (I did not open beyond removing the palm rest to get to the power switch). 

I also tried using an E-Dock.  When docked the power switch on the dock does not power on or power off the laptop either.  Same symptoms as with the power switch on the laptop.

Everything else on the laptop seems to work just fine.  Not sure what to do next with this.  Sad part is this started about 4 weeks after the Dell service expired.