External monitor flickers when laptop's plugged in

Howdy.  I have a new Latitude E6410 w/ the default Intel onboard video card, and I use an external monitor to extend my Windows desktop.  The problem is that the external LCD continually flickers whenever the laptop's power adapter is plugged in.

I've tested it with two monitors, and I've tested each of those monitors with a different Dell laptop on the same desk.  The monitors and the location are fine - it's specific to the E6410.

I've confirmed that the video card driver is the most current version, and I've installed the driver specific to one of the monitors (a Dell e1910).  I've adjusted the screen refresh rate to each of the possible settings - it doesn't help.

Any ideas?

Thanks you kindly.