I am trying to complete the GI Blues quest but the NCR just won't have it.

Info:

I have already spoken to the Dr in the Mormon Fort and the Lt at the food bank. I mention the Dr to the Lt
and get the whole story.
I reported back to The King, told Pacer to take a hike, told The King about the ambushed messenger.
I got the go from The King to negotiate with the NCR to defuse the situation.
But the NCR is hostile as soon as I arrive at the train station where Pacer is cowering at the bus stop.

Nothing I do will make them not be hostile and stop shooting me to a bloody pulp.

I have tried walking in armed and disarming myself (and lowering my hands).
I have tried walking in unarmed.
I have tried walking in unarmed, arming myself and then disarming.

It's the same every time. Someone says 'Lower your weapon or we will fire on you.' or words to that effect.
Only problem is they are ALREADY firing on me and won't stop. The Lt won't speak to me and just stands there
carving chunks outta my hide with her firearm.

I am NOT wearing any faction armor. I do NOT fire my weapon at any time. I am liked by the NCR and in
fact have never fired on or killed any NCR personnel.

I have gone back as far as the beginning of the GI Blues quest to start over and do things in different
order but the results are the same.

Any ideas?

Have you tried having your weapon holstered before you even load into the area?

only 2 possiblity

1 ) you accidently shot NCR

2 ) what uniform you wear ? brotherhood ? Caesar ?

Hmmmmm, no will give that a go tonight. TIA though confidence on this is not high...

Please re-read my OP.

"I am NOT wearing any faction armor. I do NOT fire my weapon at any time. I am liked by the NCR and in
fact have never fired on or killed any NCR personnel."

Any companions with you? NCR sometimes fire on ED-E for no reason.

I do it exactly the way you describe except I shake down Pacer then rat him out anyway. The Lt talks to me and I can convince her the King is cool.

No, I left ED-E and Cass at the King's place when I went to negotiate just in case there WAS any shooting so they wouldn't fire on the NCR by mistake.
And I tried it both ways, shaking Pacer down for caps and just telling him I was going to tell the King.

Are the NCR marked red or green via your HUD when you first approach them? They are red for me as soon as I get close enough to see them on my HUD.

Well it seems like you've nearly ran out of options. The only thing I can suggest is to try putting ON faction armor, and in this case, put on some NCR armor.
You can find some in the second tent in Primm inside a Footlocker.

They're non-hostile when they show up on my HUD. But I don't run around with my weapon drawn.

Heh, I just killed them. Then ran around and did a bunch of missions for the NCR and that got me back in their good books.
Admittedly, it was early in the game, I think I was only level 10 or 11 when I did the GI Blues quest.