A family of Microsoft word processing software products for creating web, email, and print documents.
Is this an issue with New documents as well?
Do you have retina display monitor?
If so, check these links below:
http://blog.officeformac.com/retina-display-support-is-here-for-office-for-mac-2011/
http://support.microsoft.com/kb/2742588/en-us
Make sure Office for Mac 2011 is up-to-date:
http://www.microsoft.com/mac/downloads
If its an issue with one document, remove and re-add the graphs.
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