Hi ska234,

re:
> and when I try to draw curves through the cube,
> it cuts either nothing, or strange results.

Could you please post an attachment of the 3DM files with the cube and curves you've drawn so I can take a look at your geometry?

That will help a lot to better diagnose what's going wrong with those cases, it's a lot easier to tell what's going on when I'm able to examine your objects, repeat the boolean steps, look at things from different angles, zoom in, etc...

- Michael