I tried searching forum and seems other have same problem:
in
http://fritzing.org/forum/thread/1334/?page=last#post6414
@joneff author says:
I've been having trouble with the "no copper layer defined" -error
Breadboard and schema SVG import from Inkscape work perfectly. But PCB SVG import fails with "there is no copper layer definec" ... although there is.
I got it to work, and here are my workarounds:
1) if the SVG is in mm, the PCB image will be off-scale. Apparently the import doesn't check for units. This problem only for the PCB svg.
2) the copper layer has to be described in the .svg with two nested tags like this
...
I do not know why a single tag with id=copper doesnt suffice, but this is how I got it to import.