Spoke too soon. Encountered 3 storyline bugs, each on their own potentially game breaking, but together they are certainly game breaking.
1. I was trying to deal with the Great Khans. One of the sub-tasks was to talk to commander moore about making peace between the khans and the NCR. I went there, and the only option available was that “they won’t be bothering anyone further” and it pushed me to the next part of the storyline.
2. After this, I went back and started on the House storyline again, since the NCR and House storylines had converged. I told the NCR i had finished the mission, then went and told House I had finished the mission and I got the House 5 mission. While working on this, I suddenly failed it when I was nowhere near either house or the ncr, down exploring a vault. This left me with no way to continue either the NCR or House storylines.
3. My last option then was to do the Wildcard quests. I talked to yesman, finished one of the wildcard quests, then disabled house and moved yesman into the mainframe. It did a quick check and found that I had already done the next step in his quest chain, so it didn’t give me the Wildcard: You and what army quest… This left me stuck. I couldn’t proceed with any of the 4 factions. I’m in an unwinnable state…
I suppose I should load my saved game from right before I reported in to the NCR and see if that will let me finish their quest line…