Connection to a network document is lost in the 2007 Office system or in Office 2010 after the computer resumes from standby
KB Article: https://support.microsoft.com/kb/2626998
Consider the following scenario. You access a 2007 Microsoft Office system or Microsoft Office 2010 document that is located on a network share. Your computer enters standby. Then, you resume the computer from standby. In this scenario, you receive an error message. For example, if you are working with Office Word, the error message resembles the following:
Word cannot establish a network connection with this document after the system resumed from suspend mode. Save the document into a different file to keep any changes.
Additionally, you cannot update the document and then save it back to the network share when the network location is available.