I believe I've proven my theory correct and have fixed it.
For starters, I've read many posts on the internet about resetting pram, deleting your network location, re-establishing you network etc. but after trying them, never once was I prompted to enter the password for my network. This tells me that my network password and configuration was stored somewhere.
That somewhere was keychain. Go to your Spotlight (magnifying glass in the upper right hand corner) and type keychain and you will see "Keychain Access". Click on it to enter Keychain Access.
In Keychain Access I noticed duplicate entries of my network in both system and login. Click on Login, then sort by Kind and you will see "Airport network password" for every network you belong to. Now delete the one you are having issues with as well if there are duplicate entries. If there are, this is most likely your problem. Now click on System and delete the one you are having issues with as well if there are duplicates. Once again, if there are, this is most likely your problem.
Close Keychain Access and click your WiFi Icon in the upper right hand corner and then click on the network you want to connect to. It should prompt you for a password, fill it in and then click on remember. Viola! Fixed!
I've made it sleep, I've shut down completely and now it just works.....like I am used to.
Let me know how you make out. Just because this fixed it for me does not mean it will work for everyone as our problems could be very different.
