I am trying to figure out why my navi buttons are all greyed out.  I'm stopped, parking brake pulled....

I've no specific knowledge about D series, but it isn't clear from your post whether it ever worked in your car. What else can you tell to help diagnose the problem. I does sound like an installation problem.

Yeah It did work in the car.  The original AVIC-D3 installed in the car - had a malfunctioning DVD player, mechanism broken, navi system would not work.  I know before the DVD system broke, all those buttons were working OK

I bought a working used D3 unit.  I unplugged all from the old unit, installed the "new" unit (basically took 15 mins).  Everything is working expect the navi buttons are all greyed out, cant input an address, etc..

OK, as I said I've no experience with the  D series, but it does sound like a problem detecting the parking brake.  On the Z series, Settings/NAVI Settings qill show the status of several external inputs - including the parking brake (On or Off). Hopefully your D series also has a similar status display in the Settings. If so it will tell you whether the system thinks the parking brake is set. I'm just guessing here but it is possible your previous Navi was hacked to bypass the parking brake and the replacement isn't. So I'd look for info on how that is done on your unit.

Ok, you're correct about the status messages.  It indeed states it is not receiving a parking brake on signal.  I have done the "hack" repositioning the mute wire and then grounding it with the green wire... no worky still 

I am scratching my head here.

Thanks so far.

May or may not be related. 
When I got my 4500, I purchased the parking brake bypass and installed it on my unit. Worked great then on down the road eventually I started getting notices on the unit that the parking brake was not engaged, even if it was a function that didn’t need it engaged. Nothing had changed, I hadn’t moved the unit or the wiring. Then other things started happening untill the unit didn’t work any more. Turns out it was the firmware issue. I replaced the firmware and now all is well. Hope that is not the problem but something to think about. 

Ok, finally figured out the problem here.  The dang e-brake switch was broken!  Replaced and... the greyed-out buttons are gone.  thanks for the help!