Table tools buttons not showing after change from <div> to <a>

I was updating my table tools 2.1.2.dev to the latest 2.1.3 and the buttons were not showing anymore.
I merged all the changes one by one to find the culprit and this is it:

in TableTools.DEFAULTS
before:
"button": ie ? "div" : "button",
after:
"button": "a", // We really want to use buttons here, but Firefox and IE ignore the
// click on the Flash element in the button (but not mouse[in|out]).

the same for the simliar change a few lines after inside the collection.
That's the only change that breaks the button showing. Tried in Chrome and IE.
Any thoughts why would this no longer show the buttons? Maybe I need to include/change something on my datatable configuration?
This is what I have:

"oTableTools": {
"sSwfPath": "Content/copy_csv_xls_pdf.swf",
"aButtons": [{
"sExtends": "xls",
"sToolTip": "Exportar Excel",
"sButtonText": ""
}, {
"sExtends": "pdf",
"sToolTip": "Exportar PDF",
"sButtonText": ""
}]
}
Any help would be appreciated.
Thanks in advance.