Wireless not connecting. My wireless which was working fine now won't connect to any of the

Question

My wireless which was working fine now won't connect to any of the wireless networks it used to even though they seem to be working - I just get a red cross on the icon and a message saying connection not available. If I try to reconnect and tick the box to allow connection to non secure network it doesn't seem to do anything or make a difference. I know this is a vague description but thought it might be an obvious thing. The only change I've made recently was to upgrade Adobe... Any ideas?