Cut scenes and dialogue lines always end prematurely

All my cut scenes and conversations in the single player HotS end about half a second too soon. For example, during dialogues, person B starts talking while person A is still speaking out his last word from the previous sentence. Cut scenes also end prematurely, as I can tell from the background music, and sometimes the last word of the speech, being cut.

This is really annoying. Is there anyone else experiencing the same problem? How can I fix it?