I am not the original poster but have a similar problem with a Westell 7500. At first I connected fine; went to friend's house, connected fine; came home, connected fine for a few hours then . . . nothing.
Now, it says Signal Strength Excellent, Link speed 5 Mbps, but says there is an error in connection--unable to connect to the selected access point--please check the password. I have absolutely no doubt that I am using the correct password.
We do have other wireless devices--probably more than we are supposed to, but I have tried when NONE of the others is connected and get the same thing. I am considering returning the Kindle.