I found that disable logging on provider and consumers solved most of my problems. in addition you should check the number of waiters and increase the number of threads if required.
This is not a solution, this is a workaround. The underlying problem should be investigated and resolved. If you've seen this, you should have filed an ITS.
--Quanah -- Quanah Gibson-Mount Principal Software Engineer Zimbra, Inc -------------------- Zimbra :: the leader in open source messaging and collaboration