Thanks for your help.
I managed to find my problem. I actually need to accept dragMoveEvent which is the type of Drag action that emit a TextBrowser when you drag and drop a file from your desktop onto your QTextBrowser.
For information (action 2)
http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qt.html#DropAction-enum
Just by adding the following code it work well.
@
def dragMoveEvent(self, inEvent):
"""
Need to accept DragMove to catch drop for TextBrowser
"""
inEvent.accept()
@
Thanks all