Do you have threads locked in a state that looks like this?
java.lang.Thread.State: WAITING at java.lang.Object.wait(Native Method) - waiting on <26457185> (a java.util.HashMap) at java.lang.Object.wait(Object.java:485) at java.net.InetAddress.checkLookupTable(InetAddress.java:1267)
This usually happens when the applications trying to use IPv6, when the environment is really only configured for IPv4.
The solution is to configure the the Java processes to prefer the IPv4 stack. The default is to prefer the IPv6 stack. This can be done by specifying a JVM argument to prefer IPv4.
A detailed explanation of this problem can be found here: http://wiki.zimbra.com/wiki/Configuring_for_IPv4