IllegalMonitorStateException on close brace

Question

(package names shortened to make post prettier)
java.lang.IllegalMonitorStateException
at com...ThreadPool.finishedWork(ThreadPool.java:553)
at com...ThreadPool.access$1000(ThreadPool.java:27)
at com...ThreadPool$PoolThread.run(ThreadPool.java:752)
at java.lang.Thread.run(Unknown Source)
We get these type of errors in our product.. but we don't know why..:(
workingThreads is declared like this:
private TreeMap workingThreads = new TreeMap();
And is never assigned to a new object anywhere in the code.
private void finishedWork(Date timeToKill) {
synchronized(workingThreads) {
workingThreads.remove(timeToKill); // remove a thread
} <-------Exception thrown here
at com...ThreadPool.access$1000(ThreadPool.java:27)
This part of the stack trace isn't always present... but the exception occuring at the end of the synchronizes close brace always is. It doesn't always happen in this method... sometimes it happens in other classes that synchronize on member variables.
Ideas? questions? comments? help!!!?!?!

Answer 1

Maybe you could post all the code in a synchronized
block that gives you trouble and the full stack trace?
synchronized(  tpLock  ) {
                if( (objId != null) && (!objId.equals("")) ) {
                    SnmpContainer old = (SnmpContainer)goodOnes.put( m_ip, sc );
                    if( old == null  || !old.equals(sc) ) {
                        m_changedIps.add(m_ip);
                else {  // it's a bad ip
                    goodOnes.remove( m_ip );
                if (m_changedIps.contains(m_ip)) {
                    postEvent( sc );
                    m_changedIps.remove(m_ip);
            } <--- Exception hereDoing a search for tpLock shows that other then the declaration..it only appears as "synchronized (tpLock)"
postEvent isn't in the stackTrace... and has no .waits/.notifys
So this case... plus the first posting.. are very similar.. an exception being thrown on the close brace..:(
Any trees I should be barking up?