This was one of those stupidly confident leaps of faith. I declared my arrays and at the same time set them to equal the value of the variable (u, i). I wonder if this is a source of problem? (Probably not, since the array does not show a problem in the debug output.)

Code:
var myXArray:Array = new Array;
myXArray=[u];
var myYArray:Array = new Array;
myYArray=[i];
This seems logical, but I have learned to doubt that basis.