OWC11 chart category values repeated

[Cooper]

I'm creating a chart via C#

I've got 3 series to display for a given project.
Series #1: Data spans all dates for the project
Series #2: Data spans the first half of the project dates
Series #3: Data spans the 2nd half of the project dates

Problem: Add Series #1: Data is correct
Add Series #2: The dates are repeated after Series #1's dates
Ex: jan 2007, feb 2007, mar 2007, jan 2007, feb 2007...

I've tried using the same list of dates as the category for all series and
using different categories with just the specific series' dates.

What am I missing?
TIA