Can't edit Excel file

[Mac]

1. If I open an existing Excel file, then double click any
place on the file ( want to edit
the file ), then I will immeduately get the following
error message: Excel.exe has generated
errors and will be closed by windows.

2. I can create a new file and than edit it without any
problems.

3. If I open the Excel application first, then double
click and open an existing Excel file,
I can edit it without problem also.

Is there any thing I can do to fix it?

Thank you very much for your help.

Mac