OK! So there IS an explanation. I should have been more intuitive but you came through. Good troubleshooting and yes, it is related to a poorly regulated or poorly RFI protected power supply. The disturbance isn't enough to cause the laptop any grief, but due to the highly sensitive circuitry that determines finger locations on the screen of the phone, even the tiniest disturbance in the voltages can cause the screen to "see" presses that aren't happening and cause "ghost typing".
So now my recommendations to stay away from Motorola approved chargers extends to external chargers for other devices which may contribute to subsequent problems with the RAZR while connected via USB.
I would be EXTRA CAREFUL not to use the USB connection while the LAPTOP CHARGER is plugged in, not just to prevent erratic screen issues, but also to prevent the phone from doing things you might just later regret like, calling your boss's cell phone at 3:00am while you're sitting up in bed and doing a data transfer, or accidently deleting something from memory or an email account that is unrecoverable and crucial to your job, wife, home, survival, etc...