I've played the game without problems or lag until now, but when I understood the morse code and opened the gate Overture started lagging and it doesn't help if I restart my computer. I've minimum graphics and Post effects turned OFF.
computer specs? Driver versions?
I have the latest update for my ATI Radeon 9600 pro 256mb, 1.3Gb RAM and Intel Pentium IV 3Ghz processor and I also have the patch for the game.
Could try finding a save that's just past that area. Might just be a bug for that area and nothing else.