We have had this issue for awhile and the fix was always to change the Trust Center center settings to Enable Trust Center Logging and to Enable the Developer Macro Setting to "Trust access to the VBA project object mode". I have now run into a user where that fix doesn't work.
I had the user log onto SAP from my machine and try to export. He didn't have the issue. The export worked as it should. We compare all his Excel settings with mine. They matched up. He still gets a blank excel document within SAP on his machine.
We are both on Windows 7, Excel 2007 and SAP GUI 730.