I just tried it in Carrara Time-Line window & it seems to work OK. Disregard the storyboard thing for creating the effect. In the time-line add the explosion property where you want it to start (move the verticle time line marker to that point first, hilight your object, go to properties window, click + to add explosion, set completion to 0%). Then move your veticle time line marker to end of explosion sequence & change the completion proerty to 100%.