Since a year or two I regularly see an exclamation point on the WIFI airport when I try to connect to new wireless networks. I have tried many things like restarting the computer, turning it off entirely, go through diagnostics, try to set up with assistant, but nothing helps, until eventually, if I am lucky, my mac will accept the wireless signal. Sometimes it will not and I am unable to connect to the internet. Is there anything that can be done to solve this problem?
MacBook Pro (13-inch Mid 2010), OS X Mountain Lion (10.8.2)