Index: src/java/org/apache/poi/util/POILogFactory.java
===================================================================
--- src/java/org/apache/poi/util/POILogFactory.java	(revision 638345)
+++ src/java/org/apache/poi/util/POILogFactory.java	(working copy)
@@ -36,7 +36,12 @@
     // map of POILogger instances, with classes as keys
     private static Map          _loggers = new HashMap();;
 
+    // logger implementation class to use, most often will be null
+    private static String _loggerClassName = System.getProperty("org.apache.poi.util.POILogger");
 
+    // default logger to use when nothing else is specified
+    private static  POILogger _defaultLogger = new NullLogger();
+
     /**
      * construct a POILogFactory.
      */
@@ -70,25 +75,33 @@
     {
         POILogger logger = null;
 
-        if (_loggers.containsKey(cat))
+        if (_loggerClassName == null)
         {
-            logger = ( POILogger ) _loggers.get(cat);
+            // Use the default logger if nothing else is specified
+            // It is threadsafe and doesn't care about cateogries
+            logger = _defaultLogger;
         }
         else
         {
-            try{
-              String loggerClassName = System.getProperty("org.apache.poi.util.POILogger");
-              Class loggerClass = Class.forName(loggerClassName);
-              logger = ( POILogger ) loggerClass.newInstance();
+            // This is not threadsafe, but is only lightly
+            // used for debugging poi itself
+            if (_loggers.containsKey(cat))
+            {
+                logger = ( POILogger ) _loggers.get(cat);
             }
-            catch(Exception e){
-            
-              logger = new NullLogger();
+            else
+            {
+                try{
+                    Class loggerClass = Class.forName(_loggerClassName);
+                    logger = ( POILogger ) loggerClass.newInstance();
+                    logger.initialize(cat);
+                }
+                catch(Exception e){
+                    logger = _defaultLogger;
+                }
+                
+                _loggers.put(cat, logger);
             }
-            
-            logger.initialize(cat);
-            
-            _loggers.put(cat, logger);
         }
         return logger;
     }