It's odd as it doesn`t happen all the time. For example my mobile would not connect at all last week but today after not being in the office for a few days it connected straight away. It is almost like the wifi has a dodgy lease on the ip which clears out after a day or two.

Thanks for the help.

do you have the firewall on with DDOS protection? In the past I had issues when UDP filtering was on which resulted in the exact same behavior. Admittedly that was a couple of years ago and with a 2860, still might be worth a try