Thread Local memory leaks on restart

Restarting solr (via a changed to a watched resource or via manager app for example) after submitting documents with Solr-Cell, gives the following message (many many times), and causes Tomcat to shutdown completely.

SEVERE: The web application [/solr] created a ThreadLocal with key of type [org.
apache.solr.common.util.DateUtil.ThreadLocalDateFormat] (value [org.apache.solr.
common.util.DateUtil$ThreadLocalDateFormat@dc30dfa]) and a value of type [java.t
ext.SimpleDateFormat] (value [java.text.SimpleDateFormat@5af7aed5]) but failed t
o remove it when the web application was stopped. Threads are going to be renewe
d over time to try and avoid a probable memory leak.
Feb 10, 2011 7:17:53 AM org.apache.catalina.loader.WebappClassLoader checkThread
LocalMapForLeaks