I have a file that was sent to me from a friend, and it was saved as .svg, but wouldn’t open in Inkscape.
I attempted to both, open it directly, and to “import” it, with no success. So I opened it up in notepad++ and found that it was generated with Adobe Illustrator 11. Armed with that information I renamed the extension to .ai.svg, which I had previously noticed was a special import option in Inkscape. Once it was named as .ai.svg it imported just fine using the Adobe SVG import option.
I just thought I’d share this tidbit in case anyone else runs into it. It was a super simple work around, and now I can tweak the SVG in inkscape.