iMac wireless, or software problem?

Hello, I have a late 2010 21 inch iMac. It has been working perfectly, up until recently. Over the past month and a half or so, then the wifi has started to cut out occasionally. I have dual band wireless router, and I always run it on the wireless N 5.6 Gigahertz channel. I will start using the mac and using the internet and everything will be running perfectly on it, and all of the sudden, all internet related programs will stop loading. iTunes will not work, and Chrome, Firefox, or Safari will not load. While this is happening, then the wireless settings will say that it is still connected to the wireless network. One thing that I have found to make it start working again is to switch to the wireless G 2.4 Gigahertz channel on my router, and then it begins to work perfectly again. If I stay connected to the wireless G for a few minutes then try to connect to the wireless N again, then the wireless N works just fine. Is this just a software problem, or is the wireless card in my imac going bad and or having problems?I know that it is only on my iMac and not a problem with the router, because while the problem is happening, then I have tried the internet on my MacBook, and everything is working just fine. Any ideas as to what might be wrong?

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