Increase your open file count in linux. Or tell your host to increase the file count on their server. Or (not sure about this one) if you use mcmmo, make sure it's up to date. (or even remove it) http://thedaneshproject.com/posts/how-to-increase-total-file-descriptors-count-on-linux/
My file descriptor count is high already. I removed all plugin jars, and still does that error. Any ideas? I need it fixed ASAP