laptop suddenly cannot connect to my wireless network

My 6 month old i7 Samsung laptop with windows 7 has suddenly stopped connecting wirelessly to my router (HG 520b Echolife). I have done numerous checks with my IP address within the basic function and everything appears fine. WLAN settings all fine.My laptop will connect fine direct to the ethernet connection in the back of the router and works fine from there. When I disconnect and try wirelessly, it indicates a strong signal on my network but when I try to connect (with the correct security code etc) it goes it to windows troubleshooter and fails every time. My friends android phone allows my laptop to connect to his wireless network?? and his phone can access my network from the same router. I am totally baffled about this. Can any one help with this?? I forgot to mention it had connected fine for at least 6 months.