"The file ______.docx cannot be opened because there are problems with the contents."

That sounds like document corruption. It is relatively rare these days, but there still are situtaions when it happens.

Just to confirm: You are using Word 2010. Are you inserting equations and pictures into the document? That is one known source of corruption in 2010.  Have you appliced Office Service Pack1?  That mostly fixes that source of corruption. However, your error does not sound like this type of error.

Has the document been opened in any other word processor or other computer?

Has the file been stored on a USB Thumb drive? If you are editing the file directly ON the thumb drive and do not properly shut down the drive before pulling it out, you stand a good chance of leaving part of the file behind on the HD, corrupting the document.

Here are some possible techniques you can try to fix corruption. But if it is the USB problem, you are probably SOOL because apparently the document structure puts the text content at the end of the file where it is most likely to be lost.

Trouble shooting damaged documents in Word for Windows

http://support.microsoft.com/kb/87856  -Last Review: November 16, 2006 - Revision: 2.1

http://word.tips.net/Pages/T003798_Determining_if_a_Document_is_Corrupt.html

http://www.saveofficedata.com/

This site has several tools for reading damage Office files.

DOCX format is based on ZIP format.  If the ZIP format document is corrupt and cannot be opened in Word 2007, this tool will extract text.

http://blogs.techrepublic.com.com/10things/?p=952&tag=nl.e056 

http://word.tips.net/Pages/T001513_Recovering_Corrupt_Document_Files_with_StarOffice.html

     Use System Restore  http://www.howtogeek.com/56891/use-windows-7s-previous-versions-to-go-back-in-time-and-save-your-files/

	Q87856 - Troubleshooting Damaged Documents in Word 97 for Windows (Knowledge Base)
	How to troubleshoot damaged documents in Word 2007 and in Word 2010 (Knowledge Base)
	How can I recover a corrupt document and why did it become corrupt? MVP Dave Rado on the MVP FAQ site.
	Fixing Broken Word Documents by Kate Evert at Microsystems
	Microsoft Word 2010 Bible by Herb Tyson, MVP
	Potential Causes of DOCX Corruption - Problems saving to USB Devices http://social.answers.microsoft.com/Forums/en-US/wordcreate/thread/73a1e1b0-e6cf-43b8-a97f-0b01b5c33da3/
	This chapter in Word format

http://social.answers.microsoft.com/Forums/en-US/wordcreate/thread/73a1e1b0-e6cf-43b8-a97f-0b01b5c33da3/

You could start by trying Open and Repair. In Word's Open dialog, select the document, then click the arrow beside the Open button and choose Open and Repair.