With CS5, some things have changed

FWIW,

Here's a general purpose function which gives pre-CS5 behavior for getting items by label using Dave's versioning method:

function GetItemFromCollection(label,collection){
    var scriptVersion = app.scriptPreferences.version;
    if( parseFloat(scriptVersion) > 6){app.scriptPreferences.version = 6}
    var items = collection.item(label).getElements();
    app.scriptPreferences.version = scriptVersion;
    if(items.length==0){return null}
    if(items.length==1){return items[0]}
    return items;
}

To use it you'd do something like this:

items = GetItemFromCollection("test",app.documents[0].pageItems);

If you prefer prototype methods, you can use a function like this:

PageItems.prototype.itemByLabel = function(label){
    var scriptVersion = app.scriptPreferences.version;
    if( parseFloat(scriptVersion) > 6){app.scriptPreferences.version = 6}
    var items = this.item(label).getElements();
    app.scriptPreferences.version = scriptVersion;
    if(items.length==0){return null}
    if(items.length==1){return items[0]}
    return items;
}

However keep in mind that you'd need to do this for each type of collection, and you cannot create prototype functions on collections until you initialize the collection. To do that you'd need to insert a line like this (assuming there's a document open):

app.documents[0].pageItems

You could then write:

items = doc.pageItems.itemByLabel("test");

Harbs