Here’s what worked for me:
Open Finder.
From the Menu at the top, choose ‘Go’ -> ‘Computer’.
Open your hard drive (probably called ‘Macintosh HD’).
Open the ‘Library’ folder.
Open the ‘Preferences’ folder.
Locate the ‘SystemConfiguration’ folder (likely at the bottom).
Drag this folder to your desktop (as far as I can tell, this is to back it up incase something goes wrong)
Once the copy is complete, drag the original to the trash.
In Finder, open Applications (If you don’t have it on the sideback, use ‘Go’ -> ‘Applications’).
Open the ‘Utilities’ folder.
Open ‘Keychain Access’.
Select ‘login’ from the list of Keychains.
In the list to the right, locate an object with the name of your wireless network.
Select it and press ‘delete’ on your keyboard.
Select ‘System’ from the list of Keychains.
Repeat steps 13 and 14 above.
Restart your MacBook.
Once your computer has restarted, connect to your wireless network.
