jqGrid with an editable checkbox column

To allow the checkboxes to always be click-able, use the checkbox formatter’s disabled property:

{ name: 'MyCol', index: 'MyCol', 
  editable:true, edittype:'checkbox', editoptions: { value:"True:False"}, 
  formatter: "checkbox", formatoptions: {disabled : false} , ...

To answer your second question, you will have to setup an event handler for the checkboxes, such that when one is clicked a function is called to, for example, send an AJAX POST to the server. Here is some example code to get you started. You can add this to the loadComplete event:

    // Assuming check box is your only input field:
    jQuery(".jqgrow td input").each(function(){
        jQuery(this).click(function(){
            // POST your data here...
        });
    });