Since I can't tell from the test suite, do you wrap around the matrix when you are calculating the products? For example, when doing the products of four consecutive numbers in the up/down direction, do you do rows 1:4, 2:5, 3:6, 4:7...7:10 and stop there, or do you include the row combinations [8:10 1], [9:10 1:2] and [10 1:3]?

Just submitted my solution (slightly modified from the original Project Euler problem! :-), and the values do not wrap around in any direction.

I vaguely remember there was an earlier problem exactly the same as this one on Cody, and I solved that problem some time ago. But couldn't find the old problem....