This box is just a warning because the dll file had been changed. When you see it, just restart msn and that'll work.
But this time you shouldn't have the "active = -1" error, since I removed the error message O_o
Maybe I uploaded the wrong file version. Try this one :
http://www.avesan.com/rssplug/RssPlug%20dll.rar (decompress it in your plugin directory, then launch msn. Then you'll have the warning, restart it). I checked it twice : it's the good one