I'm doing "For The Republic II" and I need to take out the Brotherhood, but everytime I go to take out the L2 part, it freezes as soon as I get there it freezes, I can't even press the guide button. AND before I got in there I needed to do a very hard lock to get in. It all happened after I helped the NCR Ranger.

Mine didn't freeze at that point but once I enter that part of the bunker my saves corrupt thereafter.

you dont need to take out the BoS.. you can convince them to help NCR for the Hoover dam battle

A bit too late I think, I've already killed almost everyone apart from the actual L2 thing.