D620 Will Not Boot Up When Connected to A/C Power??

Hello All,

I have a D620 with a Dell docking station that has worked well for years.  This morning, the external monitor wouldn't work.  The computer was frozen and would not reboot while docked.  It works great when undocked and I can even connect the external monitor directly to the laptop and it works fine.  The problem is, when it is docked OR when the AC power cord is plugged in, the video goes blank (black) and it won't come back without a hard boot.  It will also not boot up while connected to A/C (docked or just the adapter plugged into the laptop).  The voltage from the adapter is correct at approximately 20 vdc (measured).  Seems to be an issue with the laptop itself.

Has anybody had this problem?  Any help would be greatly appreciated.  Thanks

Just to make this a little simpler...

When I plug my A/C adapter into my laptop, the screen goes blank and will not come back until the A/C is unplugged and the laptop is hard booted.  The same problem occurs when the unit is docked.  The laptop works great on the battery.  Can anyone help?  Thanks