Getting error while working in ms word

Hi
I have a word file contains more than 100 pages.It will open normally a few times after saving it. but after 4-5 times opening the file it gives error….The file cannot be opened because there are problem with the contents Details:"The name in the end tag of the element must match the element type in the start tag.Location: Part: /word/document.xml, Line: 2, Column:809459".
