Problem: I try to start Web Sharing, File Sharing, or a similar background process in OS X and it fails. The process quits with no error message. What do I do?
Solution: Open your Applications --> Utilities folder. In there, start the Console application. This little app captures all the error messages and warnings thrown by the operating system. Try starting the process again. You should see the error message display in the console. From here, you can start figuring out what is wrong.