Could not convert javascript argument

Question

After trying to append some code to a div layer I received the following error and don't know why.

uncaught exception: [Exception... "Could not convert JavaScript argument arg 0 [nsIDOMDocumentFragment.appendChild]" nsresult: "0x80570009 (NS_ERROR_XPC_BAD_CONVERT_JS)" location: "JS frame :: http://code.jquery.com/jquery-latest.min.js :: anonymous :: line 113" data: no]

Below is the code that is causing the error. I understand there is some excessive code but I made it that way so it would be easy to build on for future features. Just looking for any suggestions for the error? Thank You! :)

 function catSelect(itm){ 

  //params for query
  var params = { 
   category: itm
  };

  var cmd = jQuery.param(params);

  $.ajax({
   async: false,
   type: "POST",
   cache: false,
   url: "views/gallery.php",
   data: cmd,
   dataType: "json",
   success: function(resp){
    if(resp.status == "ok") {
     $('#project').empty();
     //alert(resp.projects[0]);alert(resp.files[0]); alert(resp.titles[0]);
     var check = 0;
     var projGallery = new Array();
     for(var i in resp.projects){
      if(check!=resp.projects[i] || check == 0){
       projGallery[i] ='<a class="group" title="'+resp.titles[i]+'" href="images/gallery/"'+resp.files[i]+'" rel="'+resp.projects[i]+'" ><img class="group" alt="" src="../images/gallery/thumbs/"'+resp.files[i]+'"/></a>';  
      } else {
       projGallery[i] ='<a class="group" rel="'+resp.projects[i]+'" href="images/gallery/"'+resp.files[i]+'" title="'+resp.titles[i]+'"></a>';
      }
      check = resp.projects[i];
     }
     //alert(projGallery[0]);
     alert(projGallery);
     $('#project').append(projGallery);
    } else {
     alert("Failed to select projects");
    }
   }
  }); 
 }

Solution

I don't think you can append an array. Change:

$('#project').append(projGallery);

To:

$.each(projGallery, function(idx, val) {
    $('#project').append(val);
});