Help with wireless connection problem

[Airbrushkid]

I have my old Dell laptop which never had a problem with. It was fine until today when I tried to connect. I seems that the Wireless Connection Network is not connecting. There is a red X. It was working and I did not change anything so I am lossed can someone help?

I tried and reset the router it worked, but after I shut my laptop down and restarted it the Wireless Connection Network is not connecting. Why?