The bug is that Ranger Grant at the Hoover Dam is non-responsive and a bit on the edge... he is gripping his gun and gritting his teeth as if attack is imminent. Along with this, I am no longer able to fast travel anywhere.
Now for some background leading up to the issue. I completed the game by siding with Mr. House. One of House's missions required me to save the NCR president. I went to the dam, followed through with Ranger Grants instructions, discovered the engineer on the landing pad and destroyed his face after I talked him into attacking me. President lives to speak in the Mojave Wasteland another day. As I was heading out, I noticed Ranger Grant standing by his ham radio in the position I mentioned before, gripping and gritting. I thought nothing of it and went on. After carrying on with the storyline and eventually finishing the game, I loaded up an old save back before the president assassination attempt (a while before even getting the quest) and decided to remove Mr. House and side with the NCR. I loaded up Yes Man in House's system and he congratulates me on saving the president! Wait... I'm not even close to that part yet, why did he say that? I don't give it much thought and keep moving. Later in the story, I'm told by the Colonel at the Hoover Dam to remove the Brotherhood Of Steel. Already done from previous game, so we move on. Now I'm told to speak with Ranger Grant for preparations of the president's visit to the dam. Didn't I already save him, according to Yes Man? I follow my compass arrow to find Ranger Grant and it seems he is still standing outside where I left him in my previous game, gripping and gritting. He will not respond to my interaction attempts and I can not fast travel out to work on other missions.
Hopefully this either has an easy fix or is common enough that it will receive some attention. Either way, I can only think of one solution at the moment, and that is to start over at the beginning.