Re: SVG fiile won't open?
IIRC, some component or something got corrupted and needs to be removed. There are some people on this forum (I am not one of them sadly) who could manually look at your SVG file and remove the corruption, but as someone who also went through that, be aware you probably will lose some information. Not a lot, but enough to be obnoxious.
Also, when you do get a working version of the file, what you're going to want to do is open a new SVG file, then copy-paste your graphics into the new file. It's stupid, I know, but you'd be shocked how effective it is.
Re: SVG fiile won't open?
There are two tools: tidy from W3C and xmllint which can examine the SVG file and tell you where things have gone wrong. Make a backup before you start. Run the tools and use a text editor to remove snippets of XML until it runs clean. Some of the image will be missing but you should be able to save most of it.