If you time certain conversations right after the use of a nonuse item like the travel guide, you can go into an infinite loop in the game. This can be done with ALL menu oriented conversations.
Here is a save file that will make it easier to replicate: http://dl.dropbox.com/u/3990981/05-26-10%2002_08_49.save
1. Step Sam to where he would be speaking to the Moai head that controls the earth
2. Open your inventory and use the guide.
3. Click to speak with the head immediately following.
4. Right click twice to cancel both parts of Sam's dialogue. The menu for his conversation disappears and the game loops.