Check also your manifest:
Maybe you try to load an QWEB-File in data-Object

  'data': [
    'views/something.xml',
     # Wrong: 'static/src/xml/your_xml.xml'
  ],
    'qweb': [
    'static/src/xml/your_xml.xml'
  ],

Thank you very much.

I changed the code from '<template id="example_page" name="Example page" page="True"> to

<template id="example_page" name="Example page" >  and it worked. 

Check if this tag properly defined.

<odoo>

<data>

       </data>                       

</odoo>

OR

<openerp>

<data>

       </data>                       

</openerp>

Hi,

There is something wrong in the file example_widget.xml file you have added. Either it can be capital letter instead of small letter. Please update the question along with the above file or cross check the corresponding file comparing with the file in the link you refered.

Thanks