Many users are having compatibility problems with the latest version of Microsoft Office. This version introduced a new file type for the first time in 11 years. These new documents can only be natively opened by the latest version of Office on both Mac and Windows.

My recommendation is to “save down” to the older version in order to minimize problems with sharing files with other users.
Below are instructions for doing this in each of the Office 2008 applications.
In Word:
———————————————
Go to the “Word” menu
Choose “Preferences”
Click “Save”
And in the “Save Word files as:” dropdown, choose Word 97-2004 Document (.doc)
Finally, click “ok”
In Excel:
———————————————
Go to the “Excel” menu
Choose “Preferences”
Click “Compatibility”
And in the “Save files in this format:” dropdown, choose Excel 97-2004 Document (.xls)
Finally, click “ok”
In PowerPoint:
———————————————
Go to the “PowerPoint” menu
Choose “Preferences”
Click “Save”
And in the “Save PowerPoint files as:” dropdown, choose PowerPoint 97-2004 Document (.ppt)
Finally, click “ok”