I have just tried downloading the last week of data for Light Crude and it appears to be available. Presumably Dukascopy have changed the range of historical data they have available for this symbol.
What do you mean by summary? Are you referring to higher time-frames (1-minute, etc)? If so, Tickstory always downloads the most accurate/granular information (that is, ticks) and then convert them into the requested time-frame.