I have a new macbook that I purchased at the beginning of january. All of my software is up to date and all that good stuff. Well i initially installed the trial version of Microsoft office 2011, the trial ran out yesterday, rather than dropping the money to purchase 2011, which i didn't like very much, a friend of mine let me install their Microsoft office 2008 for Mac. Anyways I created several documents, word and excel documents with office 2011, well I can open all of them except one excel document, the message it gives me is "The file is corrupt and cannot be opened." then the 2nd message says, "the file might have been damaged or modified from its original format." I believe the format of this file is .XLSX, though i have another in that format that it allows me to open and edit like normal. Any suggestions?