In Eclipse, you have to point the Javadoc location to the guava-14.0-javadoc.jar
file itself, and not to the folder containing it.
In your project properties, go to Java Build Path, tab Libraries, find the entry for the guava jar and click on the little triangle on the left to unroll the jar options. Click on "Javadoc Location" and chose the "Edit..." button. Then choose "Javadoc in archive" and "External file". Write the jar file path or use the Browse button to find the jar.
You don't need to put the javadoc and the source jar in the build path.