Array of Structures in iOS

Has anyone had any problems with arrays of structures on iOS platform? I am passing an array of structures into a method. When I try to access the array I get an OutofBoundsException. I can print off the count and the LastRowIndex (and they are both valid and what I expect) but when I try and access the first element in the array it fires the exception.

My structure is pretty simple and looks like this:

red as Double
green as Double
blue as Double
start as Double

show more about what you are doing?

What does your method signature look like?