iMac having trouble finding ISP.

iMac (10.7.4) is too often slow in connecting to a link. About half the time, it is in "connecting" mode until it times out. I get a "Can't find the page" window. If I run System Preferences Diagnostic Assistance, I can see that there are three green lights on top, but it is getting hung up on ISP, which is red lit. I go through the process of selecting a network, after which I see the wi-fi reset itself. It very quickly and temporarily goes to a panel saying "No IP Address" and then pops back to "wi-fi connected". At that point, if I click on "Try Again", it will work successfully.

It MUST be the correct IP address or it would not successfully find it the second time. I do not understand why it is failing so often, nor what to do about it. Suggestions?

Thanks!

Ed Hooks

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