Cross-terrain only works for one square in the direction of the edge of the square you are in. For example, if you are at the eastern edge, you can only cross-terrain one square east. If you are at the southwestern corner, you can only cross-terrain south or west [or maybe also southwest].
I dare you to make less sense.
Are you a newbie, or do you have access to newbies?
This happened to me when I was prospecting a while ago, and I went to Kyle about it. He said it was an already know (and I don't know if it was bug based) bug and that he was working on it. He just couldn't figure it out. That was a while ago, and I'm assuming that it still isn't fixed.