In Fallout:NV, I initially was going against the NCR early on, but switched allegiances to see how their storyline played out.
All NCR troops accepted me as OK except for HELIOS ONE, where I had diverted power to all neighboring regions. They would attempt to kill me on sight, so I killed them all.
The problem is that I still have a quest open for requesting support from them....any way to complete this quest? I would have expected that it would fail once all the troops were dead...
The actual quest is 'Restoring Hope.'
Go to HELIOS One to ask about Forlorn Hope supplies.