Your guest would be my guest as well.
First I would delete the two Wifi sites in Network Preferences.
Then remove all the keychain entries that relate to this WiFi access. Click on All Items in Category, and use the search bar. They shouldn't be too hard to find.
Then go to Keychain Access menu > Keychain First Aid, enter your password, repair, and start.
I don't know if a restart is necessary at this point but it wouldn't hurt.
You will have to go back in Network Prefs and enter the user and password.
If that doesn't work:
Another possibility is that the .plist file is corrupt.
1. Hold down the option key.
2. In the Go menu in the Finder, scroll down to Library
3. In Library, find Preferences
4. In Preferences, find com.apple.systempreferences.plist and drag it to the trash
6. This generates a new .plist file, so you will have to reenter your preferences.