I had severe issues with my wi-fi. Turns out basically the way network-manager [ab]uses the wireless card causes it to be highly unreliable/unstable. The failing to connect was a big symptom for me. The end solution was to stop using network-manager and start using WICD.
Full instructions are here:
http://forums.linuxmint.com/viewtopic.php?f=49&t=171819
Laptop recognizes WiFI but fails to connect
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Before you post read how to get help. Topics in this forum are automatically closed 6 months after creation.
Re: Laptop recognizes WiFI but fails to connect
you did send me a link to the script but not the output of it, try again as per the previous posts.