Ok this is my second issue with the game in the space of an hour (and no one has even commented on the other). This one however is definately the bigger bug bug:

1) I am being VERY good to ncr and helping them at every oppotunity.
2) As explained elsewhere, House always wins quest 2 isn't completable so needs fixing
3) I am coming into the strip and go through to the third bit of strip just behind the building where the white glove society is.
4) I am wearing NCR armour so should be classed as a freindly.
5) After half a minute a "NCR trooper MP" comes up to me and says people have been talking about me, and it's bad talk, and the NCR have issue with me. He gives me the option of handing over money or they will try to beat me.
6) I refuse to hand over money, him and about six or seven others then start to use melee weapons on me, the securitrons do nothing at all to stop this.
7) I fire ONE bullet, or throw ONE punch and the Security box gatling laser my backside quicker than a one-minute burger.

Seriously wtf is this all about?????????

It actually does say that security personal will turn around and know the difference.

Erm what???

Security can see right through you. They know you are not really NCR.

Its not the bots that start the fight, it's NCR troops that i've done a lot for. Would like a more accurate response than jovial speculation!

The only thing is, when i first went in to the casino opposite mr house, they asked me to hand over my weapons. Knowing how much of a chore this makes things i said no. The dialogue option was some sort of polite refusal, but the club people became hostile (as this was not my fault i put got mode on and killed them all). Could this be part of it? If so it's still grossly unfair i had no choice, the same way i'll have to put god mod on again if theres no other solution.!

NCR troops in the strip are flagged as security. Echonite is right in what's they're saying. NCR is the 'rule of law' on the strip. So other actions (like wholesale slaughter, and failing to obey the rules of other factions), can and will cause other factions to dig into the negative rep, side if you do enough bad stuff.

Ok well its unfair but i had no choice but to kill them, they turned hostile, hell probably that alone caused the NCR to hate me! I'll have to do the only thing that will make things better... which is put on god mode, slaughter the strip and then hope there is some sort of "neutral reputation" cheat to make things ok again.

Well no, it's not unfair. It's realistic. If you go running down the street and start slaughtering members of your city council, the police aren't going to turn a blind eye even if the public hoists you onto their shoulders and throws you a party.

Factions in FoNV are very close to how they were in FO1/2, and radically different from FO3

The point is that the "city council" of your anology started trying to slaughter me first, after choosing a dialogue line that was basically a "no thanks" and not something like "i've got a gun and am going to kill you".

If you killed people in the club after you refused to disarm they were probably NCR citizens, so your reputation with them may not be that great anymore. A lot of people in the clubs are NCR citizens.