Error when previewing a media file in the media manager

Hello!

- xubuntu 10.10
- trunk 1106
- Debug log is attached

1) Start OpenLP and select the "Media" tab.
2) Open a video or audio file (I took the video files from the /resources/videos directory).
3) Preview one item (does not matter whether you double click it or press the preview button).
4) The following error message is shown, although the video will be previewed.

Traceback (most recent call last):
  File "/home/andreas/Projekte/openlp/trunk/openlp/core/lib/mediamanageritem.py", line 448, in onPreviewClick
    self.parent.previewController.addServiceItem(service_item)
  File "/home/andreas/Projekte/openlp/trunk/openlp/core/ui/slidecontroller.py", line 516, in addServiceItem
    self._processItem(item, slideno)
  File "/home/andreas/Projekte/openlp/trunk/openlp/core/ui/slidecontroller.py", line 630, in _processItem
    self.onSlideSelected()
  File "/home/andreas/Projekte/openlp/trunk/openlp/core/ui/slidecontroller.py", line 806, in onSlideSelected
    frame = self.display.image(toDisplay)
  File "/home/andreas/Projekte/openlp/trunk/openlp/core/ui/maindisplay.py", line 244, in image
    image = self.imageManager.get_image_bytes(name)
  File "/home/andreas/Projekte/openlp/trunk/openlp/core/lib/imagemanager.py", line 110, in get_image_bytes
    if not self._cache[name].image_bytes:
KeyError: u':/media/image_clapperboard.png'