I'm using the most recent versions of Drupal, Views and Taxonomy Treemenu.

The taxonomy treemenus are generating successfully, using the default view (taxonomy_router_term).

I'm having problems accessing the content when I'm NOT logged in as admin.  I'm using the default view (taxonomy_router_node) and access is set to unrestricted.

The 'authenticated user' (which I understand is everyone that is not logged in?) gets 
Fatal error: Cannot use string offset as an array in /sites/all/modules/taxonomy_treemenu/taxonomy_treemenu.module on line 2367
whereas the admin user gets to see the content.

If I give the authenticated user 'Administer Nodes' permissions I do not get the error and I do see the content, however that means that anyone can create content, which is not what I want.  Interestingly applying all create, delete, edit permissions (but NOT administer nodes) brings back the error.

This is the code.

    case "taxmenu/%/node/%/%":
        //Treemenus have no node links. To control exansion, we target the
        //parent tid link.
        $item['href'] = 'category/' . $item['page_arguments'][0]['vid'] . $item['page_arguments'][1]['parent_path'];
        break;

Specifically, line 2367 is
        $item['href'] = 'category/' . $item['page_arguments'][0]['vid'] . $item['page_arguments'][1]['parent_path'];

Logged in as admin $item['page_arguments'] returns:
Array
(
    [0] => Array
        (
            [menu_name] => menu-ol-hlp
            [title] => Online Help
            [description] => Jane Systems online help
            [vid] => 13
            [tid] => 0
            [options] => a:3:{s:6:"filter";a:0:{}s:6:"fields";a:0:{}s:4:"sort";a:1:{s:3:"nid";a:1:{s:5:"order";s:3:"ASC";}}}
        )

    [1] => Array
        (
            [0] => Array
                (
                    [tid] => 55
                    [title] => System Setup
                )

            [1] => Array
                (
                    [tid] => 68
                    [title] => Authorisation Centre
                )

            [parent_path] => /55/68
        )

    [2] => 25
)
But when I'm not logged in I get

a:3:{i:0;i:1;i:1;i:3;i:2;i:4;}
I can see that $item['page_arguments']  isn't being turned into an array, but I can't see why.   

I've been trying to trace back $router_items to see how it gets generated, but I can't seem to find it.

I'd really appreciate any help.

Thanks