I have a simple extjs (3.2.2) script and he perfectly work in browser:
Code:
var form = new Ext.form.FormPanel({
    api: {
		submit: CRM.ss.Mailer.add
	},
	fileUpload: true,
	width: 400,
	renderTo: 'test',
    items: [{
  		xtype: 'textfield',
        anchor: '100%',
      	name: 'to',
      	fieldLabel: 'To'
      },
	  new Ext.ux.form.FileUploadField({
	        allowBlank: true,
	        emptyText: 'Select an file to attach',
	        fieldLabel: 'Attachment',
	        name: 'files',
			anchor: '100%',
	        buttonText: '+'
		}), {
        xtype: 'panel', 
        buttonAlign: 'center',
		border: false,
        buttons: [
            {
            	text: 'Submit',
                handler: function(){
	                form.getForm().submit()
				}
            }
        ]
      }]
});
When i execute this script from AIR (of course with all necessary ext/air scripts) in debug i see:
Code:
TypeError: Null value

 at app:/lib/ext/ext-all-debug-w-comments.js : 39445

 at app:/lib/ext/ext-all-debug-w-comments.js : 39643

 at app:/lib/ext/ext-all-debug-w-comments.js : 39965

runCallback at app:/lib/ext/ext-all-debug-w-comments.js : 9830

cb at app:/lib/ext/ext-all-debug-w-comments.js : 9837

h at app:/lib/ext/ext-all-debug-w-comments.js : 2946

undefined at undefined : undefined
If fileUpload set to false all work ok (of course without file upload).

Any ideas?
Thanks