This is something I've always wondered about. I don't have this problem now, but back when I first got the game I had a measly Windows 95 computer. The game ran perfectly well except for one thing. At the Observatory when Bungehen explains the lifestream and all that, right when his CGI thing finished but right before the other character's commented, my game just stopped. I could run around the simulation and speak to my two other characters who all had unique lines, but I could not progress the game. I uninstalled, reinstalled, tried all different combinations of characters, but nothing worked. Figuring either the game my computer was just whacked, I gave up. About a month later I went to visit my uncle who also had a PC (it was a nicer one, but still ran Win95), installed the game, copied over my save file (remember floppies? I do), and lo and behold right when I expected the game to come to a halt, it continued on. I didn't get a chance to run around and converse with my comrades, but I was able to get the hell out of that place. I saved, copied to a floppy, and when I got back home I never had another problem with the game.
Does anyone know why this happened? When I ran around and talked to the characters they all had unique stuff to say (except Bungehen - my experience with adventure games immediately brought to my attention that maybe you have to directly on some obscure pixel to move forward, so I wasted so much time just tapping on that key and moving positions, trying to talk to him). This was such a weird error and I have no idea what could have caused it and as long as I've been in front of a computer (unfortunately) this is my biggest "WTF?!" moment.
