Bootstrap 2.3.2 modal not really a modal (2)

Question

There are similar posts to this on SO, but they don't cover the issue I am trying to solve: I am working on 508 compliance, and the issue I have is that while tabbing through the modal, the tab flow does not stay on the modal (i.e. go from the Cancel button back to the first input on the modal). Instead, the tabbing goes to the back ground. I need a way to keep the tabbing on the modal, so the user can not escape with out closing the modal. Also, I am using Bootstrap 2.3.2. Thanks.

Here is the structure of the modal:

<div class="modal hide fade x-large" tabindex="-1" data-backdrop="static" role="dialog">
<div class="modal-dialog">
    <div class="modal-content" >

        <form action="/...">        
            <div class="modal-header">                  
                <h4>Title</h4>
            </div>              
            <div class="modal-body">                                                              
                <div class="containerfluid">                                                                              
                    <div class="row-fluid columnHeaders">
                        <!-- column headers... -->
                    </div>

                    <div id="templateLanding">
                    </div>                                                                           
                </div>                                    
            </div>

            <div class="modal-footer">
                <button type="submit" class="btn btn-primary">Save</button>
                <button class="btn" data-dismiss="modal">Cancel</button>        
            </div>          
        </form>           
    </div>    
</div>