ISSUE:

"This file cannot be saved because some properties are missing or invalid" message when a user is trying to save a Word document with a Quick part, back to a SharePoint site, when the quick part has line breaks in the multi-line column content type.

CAUSE:

The problem is seen after installing an update to Office 2010 and the version of Office is 14.0.7102.5004 or higher.

SOLUTION:

Install hotfix per article 2878228  - http://support.microsoft.com/kb/2878228

The resolution is also included in the February 2014 Cumulative update for MSO.dll.