I would recommend disabling the avatar support for MSN until the next release of the IM Gateway plugin. It appears to be leaving a number of file descriptors open, eventually bringing your server to an upset state. Go into the admin console, under Gateways -> Settings, and open the Options tab for the MSN transport. Uncheck Enable buddy icons, save settings, and honestly, I'd recommend restarting Openfire as soon as is reasonable afterwards to clear up existing open file descriptors. We'll get a fix out for this in the next gateway release, which should be coming in the next couple weeks. I'm going to try to put out a beta build soon, especially considering we changed a number of things in dependency libraries that made some excellent improvements.