15 R3, 5GHz wireless issue

I've had my Alienware 15R3 for about a week - everythings been working fine and then last night the laptop suddenyl refused to connect to my 5ghz wirless network even though nothing had changed. 2ghz worked fine, I tested with other laptops and phones on the 5ghz in the house and they connected fine. When trying to connect and enter the password it either said the password was incorrect (which I know it wasn't) or it just closed the wireless window as if crashing and then reopened it again seconds later.

After googling this issue I removed the Killer drivers and software and reinstalled with the latest from the Killer website. This didn't work at first but then after a couple more reboots the 5ghz started working again. 

Annoyingly tonight the issue is back.. I know theres nothing wrong with my router or the password as all other devices are working fine. My router is an Asus RT-N66U with the latest firmware and I've tried changing channels etc.

I actually work in IT Support and I'm a bit stumped, my guess is the wireless card is faulty or the drivers are faulty. Any ideas anyone? Or has anyone had this and managed to fix it? It's really frustrating to have an issue like this so soon after buying a brand new laptop.

Thanks

Tim

P.S I can't login to the support section of the Dell website just keeps coming up with an error so asking here instead in the hope someone can help.