export to spreadsheet, why pop up a selection dialog box,

Hi there,

I am wondering if there is anyone who know why after upgrade a patch, the FAGLL03 line item display report's export to spreadsheet function will cause a pop-up dialog box to let users to choose "1.Excel (in MHTML format); 2.Star office (in ODS format); or 3.all available format"

After the users choose wrong format and click the "Always use selected format, the pop-up dialog box will never apprear.

How can we let the dialog box apprear again and reset the choose?