grass - Qgis map composer shows a huge red cross

I can show this best by a picture:

This cross also shows when I export it as raster or pdf. What is it and how can I get rid of it?

I am using Qgis 2.4 and the map was done with the help of the Grass plugin AniMove on Linux Mint.

Answer

It's caused by a picture item with an invalid or corrupt picture path. Click on the item and check the image source.