Table Tools doesn´t export pdf using fnCellRender and tabs

Hello,

I'm using datatables within jquery ui tabs and I use table tools plugin to export table data as CSV, and PDF files.

In addition I use fnCellRender to pre-process the data of the table before exporting it, so I can export the values of the html inputs included in datatables.

I see this post:
http://datatables.net/forums/discussion/3783/issue-with-tabletools-2.0-on-hidden-tabs#Form_Comment

and I use the code suggested in this tutorial:

http://iksela.tumblr.com/post/3445022287/using-jquery-ui-tabs-and-datatables-tabletools

but the pdf exporting isn't working on hidden tabs. Pdf button is clickable but nothing happens when I click on it. csv and copy buttons works ok.

I think the problem is related with fnCellRender option, because if I remove this option form the code the pdf exporting works ok, but in this case I can´t export the input fields content.

Here is the initialisation code of one of my tables:

var oTableObjMensual = $('#listado_mensual').dataTable({
				"bInfo":false,
				"bFilter":false,
		  	 	"aaSorting": [],
		  	 	"bPaginate":false,
		  	 	"bAutoWidth": false,
		  	 	"sDom": '<"clear">lfrtip<"pie"T>',
				"oTableTools": {
		  	 		"aButtons": [
								{"sExtends": "copy", "sButtonText": "<?= literal("Copiar");?>","sButtonClass": "botones_pie", "mColumns": "all"},
								{"sExtends": "xls","sButtonClass": "botones_pie", "sTitle": "<?= literal("Objetivo Mensual");?>", "mColumns": "all","fnCellRender": contenido_exportarDatatable} ,
								{"sExtends": "pdf","sButtonClass": "botones_pie","sPdfOrientation": "landscape", "sTitle": "<?= literal("Objetivo Mensual");?>","sPdfSize": "tabloid","mColumns": "all",
								"fnCellRender": function ( sValue, iColumn, nTr, iDataIndex ) {
									var valueExport = "";
									var data = $(sValue)[0];
									var tag  = data.tagName;

									if(tag==='SPAN'){

										valueExport = data.innerHTML;
										
									}else if(tag==='INPUT'){

										valueExport = data.value;
									}
									
									return valueExport;
				                	} 
								}
		        				],
					"sSwfPath": "/jquery/plugins/DataTables-1.9.4/extras/TableTools-2.1.4/media/swf/copy_csv_xls_pdf.swf"
				},
		  	 	"oLanguage": {
		            "sUrl": "/jquery/plugins/DataTables-1.9.4/language/es_ES.txt"
		        } 

If anyone know the solution please help me.