Loaded Civ4 and entered a multiplayer game created by a friend. 3 humans, 3 AI. Simultaneous. Everything seemed to run fine except when I, and only I, would have to do 'anything tech related.' For example, I would discover a new tech and the popup would appear asking me what to research next. I would not be able to select anything and my game would lock. All other players would see a message that they were waiting on me. I would enter Windows Task Manager and it would report that Civ4.exe was not responding. I would cancel Civ4 from Task Manager, reload Civ4 and rejoin the game. Everything would proceed smoothly until I had to choose a new technology again, at which point I would lock. To get around this, I would select my Science Advisor and queue up a number of techs. This seemed to work fine for the most part, but one particular time I attempted this, my game locked again while looking at the tech tree.