I put a new version that I tested succesfully with r99. Also, when extracting the plugin make sure the files are directly in the socket-io-mod folder in the plugins folder, in other words you should see a runtime.js dated today in plugins\socket-io-mod. Previous versions of this plugin might have dumped the files into a folder named "socket-io", if you have that folder, delete it.
Also, if you see any old files with "(Picture-That)" in their names, you need to delete those. Those were backup copies included by accident in the previous version.