Closing a workbook, exits Excel 2007 too
 

I recently started having an issue when I close a workbook. It also then
exits Excel. I have closed using the shortcut, the button on the Quick
Access Toolbar and using the close button from the Office Button. My results
are always the same, the workbook closes and immediately exits Excel. To
continue working in Excel, I have to reopen Excel. How can I fix this issue?