Last saturday we upgraded our Zimbra NE from 5.0.22 to 5.0.23
Everything OK, as usually.

However, yesterdate (monday) we suffered two unexpected hangs of zmmaiboxd. No response from http/https/imap/imaps/pop server. So we had to restart zmmailboxd. Twice yesterday (on morning and afternoon) and twice this morning in a 30 minutes period.

We have opened a support ticket, but since we are at Europe, I'm posting here in order to check if somebody has experienced same problems and there is an easy fix for this.

JVM dump shows all threads are OK but one:
Exception in thread "btpool0-76" java.lang.IllegalStateException: Internal error
at dshaker(
at ord(
at Record(
at unwrap(
at close(
at ed(
at doIdleExpired(
at org.mortbay.thread.BoundedThreadPool$ n(
CompilerOracle: exclude com/zimbra/cs/session/SessionMap putAndPrune