Zend Regex > Route module problem

iam using zend framework to build a REST web service and i am using modules to separate my api versions, as i have mentioned here

Ex: "applications/modules/v1/controllers", "applications/modules/v2/controllers" have different set of actions and functionality. I have mentioned my default module as "v1" in my application.ini

I am using context switching along with Regex Routing as i have mentioned here in my accepted solution:

$router->addRoute(
            'route1',
            new Zend_Controller_Router_Route_Regex(
                                            'api/([^-]*)/([^-]*)\.([^-]*)', 
                                            array(
                                                'controller'   => 'index',
                                                'action'       => 'index'),
                                            array(
                                                1 => 'module',
                                                2 => 'controller',
                                                3 => 'format'
                                            )
));

This is my url: http://localhost/api/v1/tags.xml

"v1" indicates module. Now, coming to context switching, if the url has v1, it is going to v1 module's TagsController. But if the module in url is v2, i am getting an error such as:

The requested URL /pt/public/index.php/api/v2/tags.xml was not found on this server.

I could not understand why its blowing up. Is it because i have put the default module as v1? I am not able to change the module based on the url.

And this is my directory tree:

application
- modules
  - v1
    - controllers
      - TagsController.php
  - v2
    - controllers
      - TagsController.php
library

My goodness... i have figured out the solution... the controller class name in the v2 module must be "V2_TagsController", not just "TagsController". Thank God, it is working now :) See the class names for controllers below:

- application
      - modules
         - v1
            - controllers
                  - TagsController.php (class TagsController)
         - v2
            - controllers
                  - TagsController.php (class V2_TagsController)
- library