Need help with "I Put a Spell on You" quest (unmarked spoilers)

[Slurpee1138]

So I found out there's a way to save the NCR monorail by eavesdropping on Curtis's radio conversation instead of confronting and killing him. Only trouble is, I cannot seem to get his radio conversation to start no matter what I do. I follow him to the control tower in sneak mode, stealth boy and everything, make absolutely sure he never detects me, my companions are miles away, everything the guides say to do. And yet, no matter how long I wait in the tower, he never starts talking on the radio, and if I move an inch he instantly enters confrontation mode, dooming the monorail. What am I doing wrong here? How do I eavesdrop the conversation and what is preventing it from starting?

[Jawey]

Apparently, if you talk to Curtis about information being leaked from the base prior to him sneaking into the radio tower, that conversation will not appear. Just to be clear, did you ever talk to Curtis at any point during the quest?

[Slurpee1138]

Ah, unfortunately I'm pretty sure I did. Aaand my last save in which I didn't is way too far back, so I guess the monorail is doomed. Oh well.