MS Word 2007

I was working on a Word 2007 document and when I tried to open it up again it would not let me. I can’t even open a new document. It says:
“This modification is not allowed because the selection is lost.”

Does anyone know what this means, or how I can retrieve my document?

Thanks for any help.

I find that if MS word plays up with a document I use Open Office which has no problems opening any version of word or other documents.
This is a free program and worth keeping in reserve.