incompatible with Fusion

I had the same problem. It can solved modified the css. I modified McPopup style, popup-element.css

You can try to paste it code in your custom or default css theme.

/* Fixed borders of popup */
/* ---- Border ---- */

.popup-style-mcpopup .popup-element-body table.popup-layout{ margin: 0; padding: 0; position: relative; border-collapse: collapse;}
.popup-style-mcpopup .popup-element-body table.popup-layout tbody{ border: none;}
.popup-style-mcpopup .popup-element-body table.popup-layout td{ margin: 0; padding: 0;}

.popup-style-mcpopup .popup-element-body .top .left{ background: url('images/top-left.png') no-repeat; height: 55px; width: 55px; padding-left: 0px;}
.popup-style-mcpopup .popup-element-body .top .right{ background: url('images/top-right.png') no-repeat; height: 55px; width: 55px; padding-right: 55px;}
.popup-style-mcpopup .popup-element-body .top .center{ background: url('images/top.png') repeat-x top; height: 55px;}

.popup-style-mcpopup .popup-element-body .center .center{ background: url('images/back.png');}
.popup-style-mcpopup .popup-element-body div.inner{ color: #ccc; margin: -20px -15px; position: relative;}
.popup-style-mcpopup .popup-element-body div.inner a{ color: #fff; text-decoration: none;}
.popup-style-mcpopup .popup-element-body div.inner a:hover{ color: #bbb; text-decoration: underline;}
.popup-style-mcpopup .popup-element-body .center p{ margin-right:15px;}

.popup-style-mcpopup .popup-element-body a.popup-close-button{ background: url('images/close.png') left top; display: block; height: 9px; position: absolute; top: -6px; right: -11px; width: 9px; z-index: 3;}
.popup-style-mcpopup .popup-element-body a.popup-close-button:active{ background-position: left 9px;}
.popup-style-mcpopup .popup-element-body a.popup-close-button span{ display: none;}

.popup-style-mcpopup .popup-element-body .center .left{ background: url('images/left.png') repeat-y left; width: 55px; height:200px;}
.popup-style-mcpopup .popup-element-body .center .right{ background: url('images/right.png') repeat-y right; width: 55px; height:200px;  right: 55px; position:relative}

.popup-style-mcpopup .popup-element-body .bottom .left{ background: url('images/bottom-left.png') no-repeat; height: 55px; width: 55px;}
.popup-style-mcpopup .popup-element-body .bottom .right{ background: url('images/bottom-right.png') no-repeat; height: 55px; width: 55px; padding-right: 55px;}
.popup-style-mcpopup .popup-element-body .bottom .center{ background: url('images/bottom.png') repeat-x bottom;}

But i had another problem, i need to insert a fixed height to show the element body .center .right and left if i want to show lateral borders.

sorry my english (translate with google)

To remove the padding of standard styles in the classes:
.popup-style-mcpopup .popup-element-body .top .left
.popup-style-mcpopup .popup-element-body .top .right

But I do not know how to make the automatic calculation of height for the classes:
.popup-style-mcpopup .popup-element-body .center .left
.popup-style-mcpopup .popup-element-body .center .right

The heights should scale automagically.

I'm also using Fusion. I found the problem to be a conflict with the classes: left, center and right.

To fix this issue, I modified the popup-element-body.tpl.php file and replaced those classes with more specific ones, then modified the popup-element.css file for the bent_white style:

old popup-element-body.tpl.php:

<table class="popup-layout">
    <tr class="top"><td class="left"></td><td class="center"></td><td class="right"></td></tr>
    <tr class="center">
      <td class="left"></td>
      <td class="center">
        <div class="inner">
          <?php print $close; ?>
          <?php print $body; ?>
         </div>
      </td>
      <td class="right"></td>
    </tr>
    <tr class="bottom"><td class="left"></td><td class="center"></td><td class="right"></td></tr>
  </table>

new and improved:

  <table class="popup-layout">
    <tr class="top"><td class="topleft"></td><td class="topcenter"></td><td class="topright"></td></tr>
    <tr class="center">
      <td class="centerleft"></td>
      <td class="centercenter">
        <div class="inner">
          <?php print $close; ?>
          <?php print $body; ?>
         </div>
      </td>
      <td class="centerright"></td>
    </tr>
    <tr class="bottom"><td class="bottomleft"></td><td class="bottomcenter"></td><td class="bottomright"></td></tr>
  </table>

I was able to use the same modified popup-element.tpl.php file in the mcpopup style, but I had to modify the .css file in that directory separately.

None of the approachaches described above work with more recent versions of Fusion or Acquia_Prosper on D7.

Any ideas or suggestions?