After closing file, excel believes file is still open.

I have a file that is acting strange.

When I open the file, it will be appended with a :1 as though there are multiple windows open when there aren't (i.e. filename.xlsx:1).

When I close the file, it closes fine. When I go then to close the application, it prompts me to save the original document as though it were still open.

This problem progressed to the point where it wouldn't not even open at all. I've discarded that file and reverted to an earlier version that still works, but it still has the strange behavior listed above.

This is a file with multiple pivot tables and an external data source. But I've gone through the data sources, made sure they are pointing to the correct place, etc, and nothing seems strange with that. I'm using excel 2010.

Any thoughts? Much appreciated.

Joe