Windows 7 64 bit. I've played the game all the way through multiple times. Now I've developed a new glitch. SPOILER WARNING
After the big duel when the entire company is crowded into a little room and Alister comes in to complain - when I play it now, the door opens, no one is there, then it jumps my character to the dining room and Alister has disappeared from the entire game. He's not in the group. He's not at Redcliff, he's just gone visually. You can hear him, but he's gone and when the army goes to Denerim, it's just my character, Arl Eamond and his brother out in the forest outside Denerim. I can run my character all the way through burning Denerim and around, I've got screen shots of this. It's rather amazing, but there's no one else there, no darkspawn, no army of humans, no one but my character. Does anyone know how to fix this???