There are a couple of possibilities, (its probably easiest to copy the refernced svg file somewhere then rename it from .svg to .fzpz and upload it here so we can have a look at it. Something is wrong in the svg which is breaking the fritzing renderer, by default Inkscape stores in Inkscape format and you are usually better to select "plain svg" in the file type menu. Its possible that something that Inkscape added is causing the problem. The next problems is that you shouldn't modify the core parts directory as it is synced to the repository on github and thus when the next parts update is pushed your changes will be overwritten. The usual way to do this is to save as a new part in parts editor, then unzip, edit and rezip the files and use it as a new part.
