Stacked Bar Chart looses data when changing a specific horizontal axis value

Stacked-Bar-Weirdness.xlsx I have a stacked bar chart that I put together.    When I change a specific value on the horizontal axis most of the bars seem to vanish.    The values are based on a series of month/year dates.   In the attached sample, change the word "test" in Cell AW4 to the correct date (12/2010) and watch what happens to the bar charts.  They all seem to vanish except one.  I have constructed this bar chart several times and still come up with the same problem and it seems to always be the values in the vicinity of AW.