If the month range selected is between Nov 2010 to Jan 2011 then Week1 that belongs to Jan 2011 appears first in the KPI. The order is improper
Set the 'OrderBy' column in the cross-tab area of the KPI to 'DATE_KEY - Ascending' such that the Week1 that belongs to Jan 2011 appears at the end which is the correct way of looking at the data if the month range selected is between Nov 2010 to Jan 2011