title: Cannot edit content of new or existing CMS Pages
body: <p>I have just discovered that since a short while, I cannot figure out if it's a few days or a few weeks, we are unable to edit the content of new or existing CMS pages.</p>
  
  <p>I can edit the title, but not the content itself. The WYSIWYG editor buttons are not showing. When editing a static block, everything works fine.</p>
  
  <p>See here what happens:
  <a href="http://postimg.org/image/v1ib7wbcn/" rel="nofollow">http://postimg.org/image/v1ib7wbcn/</a></p>
  
  <p>System.log doesn't show anything strange. Exception.log is showing:</p>
  
  <pre><code>2016-01-11T11:20:09+00:00 ERR (3): 
  exception 'Mage_Core_Exception' with message 'Invalid blocktype: Mage_Mpblog_Block_Rss_Wrapper' in /home/scrobby/domains/scrobby.nl/public_html/app/Mage.php:594
  
  Stack trace:
  0 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Model/Layout.php(495): Mage::throwException('Invalid blocktype...')
  1 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Model/Layout.php(437): Mage_Core_Model_Layout-&gt;_getBlockInstance('mpblog/rss_wrap...', Array)
  2 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Model/Layout.php(472): Mage_Core_Model_Layout-&gt;createBlock('mpblog/rss_wrap...', 'mpblog.rss.wrap...')
  3 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Model/Layout.php(239): Mage_Core_Model_Layout-&gt;addBlock('mpblog/rss_wrap...', 'mpblog.rss.wrap...')
  4 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Model/Layout.php(205): Mage_Core_Model_Layout-&gt;_generateBlock(Object(Mage_Core_Model_Layout_Element), Object(Mage_Core_Model_Layout_Element))
  5 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Model/Layout.php(210): Mage_Core_Model_Layout-&gt;generateBlocks(Object(Mage_Core_Model_Layout_Element))
  6 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(344): Mage_Core_Model_Layout-&gt;generateBlocks()
  7 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(269): Mage_Core_Controller_Varien_Action-&gt;generateLayoutBlocks()
  8 /home/scrobby/domains/scrobby.nl/public_html/app/code/community/Magpleasure/Guestbook/controllers/IndexController.php(53): Mage_Core_Controller_Varien_Action-&gt;loadLayout()
  9 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(419): Magpleasure_Guestbook_IndexController-&gt;indexAction()
  10 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action-&gt;dispatch('index')
  11 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(176): Mage_Core_Controller_Varien_Router_Standard-&gt;match(Object(Mage_Core_Controller_Request_Http))
  12 /home/scrobby/domains/scrobby.nl/public_html/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front-&gt;dispatch()
  13 /home/scrobby/domains/scrobby.nl/public_html/app/Mage.php(683): Mage_Core_Model_App-&gt;run(Array)
  14 /home/scrobby/domains/scrobby.nl/public_html/index.php(96): Mage::run('default', 'store')
  15 {main}
  </code></pre>
  
  <p>Any thoughts?</p>