I have an imported surface that I am trying to trim. I've managed to trim the surface in one direction using a plane as the tool.

Now when I try to trim with the front plane instead of the right plane (just for instance) I get an error telling me: "Cannot partition surface, trim tool and target do not intersect."

I've tried repeating the trim with an actual planar surface instead of a plane, with the same result. The surface I'm using also clearly does intersect, and go all the way through the surface body.

Any thoughts why this is happening?

Using SolidWorks '01 btw.