I'm trying to connect my Kindle 3 to my wireless network (Cisco Linksys wireless-N broadband router) and I get the error message "unable to connect to wi-fi network. The password you entered is incorrect or invalid." I changed the password to make sure I was entering it correctly. What information is the Kindle really requesting/how do I overcome this issue?

Four reasons come to mind that may prevent you from connecting:

1. Wi-Fi Passwords are case sensitive. Please check again if you entered the password with proper casing and you did not put any extra white space in front or behind. I know, this sounds annoying, but it is really the most common cause for connection problems.
2. Give your network a unique SSID. This is the network name that shows up in the list of detected networks. Default names like LINKSYS can be troublesome if a neighbor one block down the street happens to have a router from the same company.
3. Some routers have a MAC address filter as a security measure, limiting service to devices specifically whitelisted. If your router is set up for this, add your Kindle's MAC address to the list of permitted devices. See your router's configuration under Wireless > Wireless MAC Filter. You can check the MAC of your Kindle from its settings page (press HOME, MENU, select SETTINGS, see paragraph headlined "Device Info".
   
4. There are twelve different standards for Wi-Fi transmission collected under the hood IEEE 802.11. The four most dominant transmission modes are called a, b, g and n. They differ in radio frequency, modulation method and data rate. Kindle supports the two standards IEEE 802.11 b and g only, which is not really a problem because all wireless routers I ever encountered support one or both of these, too. However, the Linksys N-series can be set up to use 802.11n exclusively, not allowing for b or g connections. In the router menu Wireless > Basic Wireless Settings (Manual Setup), make sure the network mode is configured as "Mixed".