jQuery dialog throws error

Question

I've created two plugins (A and B), where plugin B is dependent on plugin A.
In plugin A I use jQuery UI Dialog for user interaction and this works fine.

Dependency: Plugin A is a filebrowser. Clicking a button opens a dialog window where user can select file to relate to wordpress post. Plugin A loads all JS necessary to use the dialog box.

Now I try using Dialog box in plugin B and I get an error:

(this.uiDialogTitlebarCloseText = c("<span/>")).addClass("ui-icon ui-icon-closethick").text(m.closeText).appendTo is not a function

Plugin B

---

I'm testing with very simple code:

// Javascript code from custom_plugin.js
jQuery(document).ready(function() {
  jQuery('#dialog').dialog();
});  

// Code from my custom_plugin.php
<div class="icon32" id="icon-tools"><br></div>
<h2>Gallery manager</h2>

<div id="poststuff" class="metabox-holder">
  <div id="post-body">
    <div id="post-body-content">
      <div id="dialog" title="File browser"> This is a dialog.</div>                               
    </div>
  </div>       
</div>

I have no idea why I'm getting this error. Any suggestions on how I can resolve this?

Plugin A

---

This is the codeI use in plugin A. I'm getting the above error without ever interacting with plugin A.The scripts for plugin A is just loaded normally.

  jQuery("#fileBrowser").dialog({
        title: "File browser",
        modal: true,
        autoOpen: false,
        height: 700,
        width: 800,
        open: function() {
          jQuery("#fileBrowser").load("../wp-content/plugins/wp-filebrowser/fileBrowser.php", function() {

            // Clear input / feedback text when entering new folder name
            jQuery('#newDirDialog input[type=text]').focus(function() {
              jQuery(this).val('');
              jQuery('.newDirFedback').fadeOut(function(){ jQuery(this).empty(); });
            });

            // Initialize create new dir dialog window
              jQuery("#newDirDialog").dialog({ 
                autoOpen: false, modal: true, title: "New dir"
              });
          });
        }
      }
  ); 

  //Open dialog box on click from WP admin         
  jQuery('.addImage').click(function() {
    imageUrlInputBox = jQuery(this).siblings(":text");
    imagePreviewLink = jQuery(this).siblings("a");
    jQuery("#fileBrowser").dialog("open");
  });