Ooops! The array should be Int32. I don't know why it not being Int32 might cause that error, I would expect a type error. If it persists post the bit of code that causes it.
Code:
Dim routepoints(0,0) As Int32 ' in Globals
...
...
Dim routepoints (b-a+2, 2) As Int32
For i = a To b + 1
Point(i).x = (...some calculation)
routepoints(i-a,0) = Point(i).x ' so it starts from 0
Point(i).y = (...some calculation)
routepoints(i-a,1) = Point(i).y
Next
drawer.(pen.Value, routePoints())
...