Other than a possibly minor rep with NCR, I don't see any obvious reason for them to go after me. Even the Powder Gangers weren't hostile to me until I decided to help out Goodsprings!
So, reload, and use that nice Legionarre uniform so nicely given to me by the Devs in the house with the bark scorpions and the Grenade Rifle. Head Honcho there then gives me the "Cold, Cold heart" quest.
Funny thing is, I'm getting the sense that I should be able to get the quest without the armor, baised on his dialouge. Only thing that I can think of that may cause them to be hostile is that I have the "Booted" quest currently active. My guidebook, however, indicates that I should be able to waltz into the slave camp (and presumably the Legionarres at Town Hall) without causing a shootout.
Did my wonderful machine that manages to run Mothership Zeta without running into bugs finally reach it's first bug in NV? Or is this supposed to happen and it's just Dev oversight?