Also before you encounter your next problem familiarise yourself with the search button up top, it will surely provide you answers to pretty much everything.
It has to do with your command map, you have to define your top-left and bottom-right corner of your map.
Have a look at your Level Designers Reference(LDR) that came with Radiant. The Command Map section is what you want. The LDR can be found in \Program Files\Wolfenstein - Enemy Territory\Radiant-1.4\docs\Level Designers Reference\index.html
You don’t have to have a command map/shaders to test your map. But you do need the min/max coords.
gl.
[edit]yea, if you’re using 1.5, do what chr1s said 8)