My 60CSX takes maps from this site, no problem.
Please post a link to the map you are trying to load.
What map software are you using? What OS? How big is the microSD card? IIRC 4GB is the maximum size a 60CSX can handle. How big is the section you are trying to transfer?
You realize that a 60CSX will only support a single file named gmapsupp.img, but that file can contain multiple maps?