no issues connecting iPhones, iPad, laptop in any room in the house but my sons 3DS and pc will not connect. When it asks for the security key am I correctly understanding this is the wifi password it's asking for? The password gets rejected even though it's definitely the right one and is accepted on all other devices. Really frustrating
The 3DS is going to be a problem device for you as it does not support the Wireless N standard as it is only wireless B\G.
You can try setting the Hub's wireless radio to upto 54Mbps or g\n mixed mode on the 2.4Ghz band (Depending on which hub you have) and using WPA2 with AES encryption. I would bear in mind that this will slow the whole 2.4Ghz network to around 25Mbps.
What wireless adapter is the PC using.
Are the other devices that are sucessfully connecting, 5Ghz capable. If so, it might be worth trying setting these devices to use the 5GHz band exclusively.
Always worth trying to improve your wireless signal especially on the 2.4Ghz band. Downloading a wireless scanner like InSSIDer or Wifi Analyser for Android would help you select the best channel, bearing in mind the scanner will not show interference from domestic appliances like A\V streaming devices, Baby monitors, Chordless phones, Microwave ovens, Plasms TVs, Security systems etc.