Excel opening a "phantom" worksheet at random times
 

I have a user who will have a phantom Excel spreadsheet, entitled Object,
open at random times while she is trying to open another spreadsheet.

This Ojbect spreadsheet will stay open, and she can open other spreadsheets,
but the only thing that will open is the Menu bar, toolbars, and the status
bar. The file itself doesn't open, the space is empty and the user can see
the desktop.

When this happens, the user has to shut down her machine, not a restart,
before she can continue on in Excel.

Any ideas?