Symptom
The form layout can not be saved unless a selection is made for which file format to use for the form.

Problem
When using Excel 2007, first time the user wants to save a new or updated form layout in Controller a pop up is displayed to select a 'File format of report'. This selection will determine in which format the Controller form layout is saved. 
 
Cause
As designed.  
 
Solution
Select one of the formats available (depending on which Excel version the Controller users will be running):
.xls - Compatible with Excel 2003.
.xlsx - Excel 2007 format, not compatible with Excel 2003 or earlier.