Document Not Saved in Excel

I have a user that about two weeks ago just out of the blue had an Excel document give the error "Document not saved" when she pushed the save button. I tried everything under the sun I could think of but nothing fixed it. The next morning it just worked and we didn't worry much more about it. Jump forward to today. It is happening again to a different file. All other Excel files are opened and saved fine except for this one. We can open it up, make changes but it won't save. We can open it up and save it on other computers just not this one.

Background: She is on a Windows 7 computer with Office 2007. It is an Office 97-03 document. It has always worked before and all other documents work fine.

Thanks!

Out of curosity, are all the documents the user is having problems with, 97-03 Office documents, and the ones the user is having no issues with, Office 2007 documents?

All of the files, whether they worked or not were 97-03 files.