Another RAMPS power/connectivity issue

I know various versions of this issue have been posted and solved, but I haven't seen this one yet and the previous fixes have not worked.

Symptoms:
Arduino connected via USB to computer -> Arduino works, computer recognizes Arduino (i.e. shows up in COM list, can upload files)
Arduino + RAMPS via USB to computer -> Arduino works, computer recognizes Arduino
Arduino + RAMPS via USB to computer + 12V to RAMPS -> Arduino (presumably) works, computer does not recognize Arduino
Arduino + RAMPS via USB to computer (w/o additional power) + Smart LCD Controller -> Arduino works (LCD display lights up and responds to inputs) , computer does not recognize Adruino (btw, I've tried removing each ribbon cable independently -- with either or both attached, PC does not recognize Arduino, but with both disconnected and with daughter board mounted to RAMPS, it does recognize Arduino)
Arduino + RAMPS via USB to computer + 12V to RAMPS + Smart LCD Controller -> Arduino works (LCD display lights up and responds to inputs), Machine works (moves responding to LCD-input commands), computer does not recognize Adruino

Essentially, right now I have to power down, remove the RAMPS shield or the Smart LCD Controller to upload new files, all motor movement must be initiated from Smart LCD Controller, and I have no way of interfacing (e.g. Pronterface) when 12V is supplied to activate motors.

I do have D1 installed (though I cannot affirm right now that it is "good")

12V supplies to RAMPS (11A and 5A) are both right at 12.0V and are wired correctly (+/-).

Any ideas on where to continue troubleshooting?

Hoping its an easy oversight -- I don't mind admitting to stupidity when that is the case.

Thanks

One other diagnostic note - the Arduino (without RAMPS or accessories) can be powered by a 12V wall adapter while also attached to the computer by USB, and the computer WILL recognize it. Thanks

I have a similar problem and ALL the forums i have visited give me no answer.Basically i need to remove the ramps 1.4 from arduino. Only then will it allow the upload of software.I connect back up then using pronterface connect.Says its connected put no temp values no axis movement nothing.
I am using arduino 0023 to upload.
Ive Tried sprinter/marlin uploaded.
Tried it with 12v power and without nothing
Checked thermistors all ok
D1 installed
I am stumped.!??!? I have checked everywhere,thus my desperation on a forum

What type of 12V power supply are you using?

I am using the xbox. 12v 206w power brick.supplying to 5a rail.blue and red to there correct pins.