One of my Windows 7 laptops will not connect to the wireless network

[#1]

Has anyone managed to solve the issue of one of their laptops/devices not connecting wirelessly?
Both my PC and both my laptops use Windows 7, all except one of the laptops connects no problem on first connection.  I have read on many forums that everyone seems to be solving it by switching off the adapter and switching it back on again, I've tried this several times but it doesn't work.
Anyone have any other ideas what it might be?
I've only just recently changed to Plusnet and never had any issues like with my last ISP, so I know the wireless adapter works fine on the laptop.

[#2]

welcome to the forums
if IPv6 is enabled on your network adapter, try disabling it.

[#3]

I tried it with this enabled and disabled, it still won't connect.

[#4]

I had a strange situation after changing a router where one device wouldn't connect wirelessly.
I solved it (don't understand why though) by changing the adapter hardware properties to turn ON "Adhoc support 802.11n" to match other systems that worked OK.