Try the folloing.

1. Open Excel.
2. Paste the following data
A B C D E F
2008 10 20 30 40 0 10


3. Menu Insert/Pie (select the first Pie type)
4. Right Click one of the top of any part of the circle/Format Data Series
5. Click Shadow and move any of the slides on the right.
See what happend on the chart.

The problem is that the ZERO generates a full circle and you can drag and drop
all the other values present in the chart but some are above and some below
the 0 full circle.

How can solve this?
How can I report this issue to Microsoft?

José.