Hi Karen, as I have only recently purchased a Mac desktop myself so I am not familiar with the problem you have highlighted; I assume that you are using the new version of OS X Yosemite where there have been certain issues with this new update. Perhaps, if you are unable to get answers on here you can raise it on the Apple Community website HERE and hope they can give you some assistance. Good luck and sorry I can't help other than to bump your thread back up to the top of the page in the hope Mac experts on here can advise you.
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Regards, Hazel