Issues with Mac OSX and BT Home Hub 5?

We recently switched to a BT Home Hub 5 in our household and I've been having problems connecting to it with my MacBook Pro (2012 Retina). Every time I tried to connect to the router with the correct password I'd get the 'invalid password' error over and over. Then suddenly it would connect but drop again and the issue would return on waking my MacBook up. I did some research and learned it could be the conflicting 2.4GHz and 5GHz wifi frequencies which the Home Hub is meant to switch between automatically. We assigned different SSIDs to the two frequencies and I can connect perfectly to the 2.4GHz one. However I still get 'invalid password' when trying to connect to the 5GHz connection. I'll also add that no other device in our house has had this problem.

So is this an issue with Mac OSX or is my laptop faulty? Alternatively, is the router doing something wrong? We can live with having two separate connections and 2.4GHz is just fine but it was my understanding I should be able to connect to 5GHz frequencies on my laptop.