Why are my audiobooks in a playlist I didn't put them?

Question

I just checked my iTunes playlists, and all my audiobooks and podcasts are in a big project folder, where I didn't put them! What's more, iTunes won't let me delete them from the folder. What's gone wrong and how do I cure the problem? The books (from Audible) are also where they SHOULD be, i.e. in Books.
(Supporting information :
Top level - 1 playlist folder, where I see all the books etc that shouldn't be there
Next level down - two folders containing smart playlists, each populated by a different field; nothing in them that shouldn't be
Bottom level - around 20+ ordinary playlists, each one sorted by the contents of Comment; nothing in them that shouldn't be
iTunes 10)

Answer 1

It sounds like you must have created an open wireless network that anybody can join. You should be able to easily remedy the situation by properly configuring your network by enabling the WPA2 security feature at a minimum so that a passord is required to join the network.
What type of network equipment do you have? If you have an Airport Extreme or Time Capsule the Airport Utility software provided by Apple makes the setup quite easy. The Airport utility can be found in the Applications/Utilities folder. If you have equipment from another vendor just Google WPA2 followed by the vendor make and model info. There are usually plenty of others that have created helpful guides.