That happens because you have asked the popup to open everytime irrespective of the link is disabled or not.
To prevent this just add a check before opening the popup.
While calling pass the id/element to know which link button called it. And in the function, check if that link is disabled or not. I have not checked this code. It should work, but do use firebug and make adjustments if it doesn't work.
javascript:return fnUserDetailsPopup(\"0}\",\"1}\", this)",Eval("FileID"),"EmailFailed
function fnUserDetailsPopup(id,type,elem) {
$('.modalbox').fancybox(
{
if($(elem).attr("disabled") != "disabled")
{
'padding': 4,
'width': 600,
'height': 300,
'scrolling': 'no',
'type': 'iframe',
'href': '../PopUps/UserCreadtedDetails.aspx?BulkFileId=' + id + '&type=' + type
}
});
return false;
}
Hope this helps!