var response = request.responseText;  // httprequest response
var jsRespObj = {};
jsRespObj = eval("(" + response + ")");
if(jsRespObj.results[0].error != null){
    alert('Hi');    // never gets to this line
}

{"results":[{"cat_id":"1","cat_name":"A cat name","treat_group":[],"error":"Test"},{"cat_id":"2","cat_name":"Another Cat Name","treat_group":[],"error":"Test"}]}

function getAll(){
    var request = google.gears.factory.create('beta.httprequest');
    request.open('GET', '/find/gearssetup/');
    
    request.onreadystatechange = function() {
    
      if (request.readyState == 4) {
    try{
            var response = request.responseText;
            var r = {};
            r = eval("(" + response + ")");    // ** Needed to Parse here too
            processAll(r);            
        }// try
        catch(ex){
            log("Error: " + ex.message);
        } // catch
      }    // readystate
    };    // onstatechange
    
    request.send();
} // getAll()

function processAll( response ){

     var jsResp = eval("(" + response + ")");    
....
....
}