There was an error in creating XML file

Hello,
I wish to store my company data in xml format. I use Office 2007 and tried to generate xml from Microsoft Excel.
But when I try to generate xml the following error message appear.
All other functionality of Excel is just fine except about XML.
If you know the solution please let me know.
Application Error
There was an error in creating XML file
Object reference not set to an instance of an object.
Wishes,
Miller
