If you’re using Mathematics tools with Microsoft Word 2007 or 2010, you may get the following error message when you save and then re-edit a document with mathematical formulas.
The file <document filename> cannot be opened because there are problems with the contents.
The error window gives the following details about the error message:
The name in the end tag of the element must match the element type in the start tag.
Here’s the description of the cause from Microsoft:
This issue is related strictly to oMath tags and occurs when a graphical object or text box is anchored to the same paragraph that contains the equation.
Basically it is because of the overlapping tags in the XML file that is created when Microsoft Word document is saved. In order to correct the issue, you only need to make sure that the oMath tags are correctly structured in the document. If you are not familiar with XML format, you may use the automatic Fix It tool from Microsoft which will automatically fix the issue and recover the document for you. You can download the Fix It tool from Microsoft. The solution of this problem is also described in KB2528942.