I've been having a lot of these slowdown issues myself but i fixed it by getting that file off these forums and it has worked but has anyone experienced any gamebreaking bugs related to quests? Like for one all of Caesar's Legion are hostile to me so I can't goto the fort which is part of the main questline and I can't even do Oh My Papa because the dialog choices don't come up with the girl at Hoover Dam. Just wondering if I'm not the only one experiencing these quest related bugs.

Did you get yesterday's patch? It supposedly fixed some quest and script bugs. I can't comment on those particular bugs, as I haven't been that far into the game--too busy working on fixing technical issues.

Yeah my Steam client automatically downloaded it yesterday and now I don't have the note from Caesar and if I goto the fort they all attack me. I even tried using a stealth boy and getting to the fort which did work but the guys at the fort attacked me too. I've tried reloading saves and restarting my client for the Oh My Papa quest but I still can't talk about creating an alliance with the Khans and NCR.