Not that i care much about IE, but it seems like an issue with its handling of xml data; will try and see if i can get it working later today.
Have you solve the problem? I have the same question that the plugin can't work well in IE.Maybe the core problem is that the IE doesn't support the function 'getElementsByTagNameNS',but how to solve?
Use the new parseJSON option and code
to achieve IE compatibility (and quicker load time). There is python script there which you can run on your gexf to create a JSON file. Then use the parseJSON plugin to load the data and it will run on IE (and other browsers)
The new version of sigma comes along with a new gexf parser working on IE 9/10/11 as per this precise commit.