I've got a Java web application (using Spring), deployed with Jetty. If I try to run it on a Windows machine everything works as expected, but if I try to run the same code on my Linux machine, it fails like this: [normal startup output] 11:16:39.657 INFO [main] org.mortbay.jetty.servlet.ServletHandler$Context.log(ServletHandler.java:1145) 16 Set web app root system property: 'webapp.root' = [/path/to/working/dir] java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.mortbay.start.Main.invokeMain(Main.java:151) at org.mortbay.start.Main.start(Main.java:476) at org.mortbay.start.Main.main(Main.java:94) Caused by: java.lang.ExceptionInInitializerError at org.springframework.web.util.Log4jWebConfigurer.initLogging(Log4jWebConfigurer.java:129) at org.springframework.web.util.Log4jConfigListener.contextInitialized(Log4jConfigListener.java:51) at org.mortbay.jetty.servlet.WebApplicationContext.doStart(WebApplicationContext.java:495) at org.mortbay.util.Container.start(Container.java:72) at org.mortbay.http.HttpServer.doStart(HttpServer.java:708) at org.mortbay.util.Container.start(Container.java:72) at org.mortbay.jetty.Server.main(Server.java:460) ... 7 more Caused by: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@15311bd for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category) (Caused by org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@15311bd for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category)) at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543) at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235) at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209) at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351) at org.springframework.util.SystemPropertyUtils.(SystemPropertyUtils.java:42) ... 14 more Caused by: org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@15311bd for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category) at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:413) at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529) ... 18 more Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/Category at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389) at java.lang.Class.getConstructor0(Class.java:2699) at java.lang.Class.getConstructor(Class.java:1657) at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:410) ... 19 more Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Category at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) ... 24 more [shutdown output] I've run the app with java -verbose:class, and according to that output, org.apache.log4j.Category is loaded from the log4j JAR in my /WEB-INF/lib, just before the first exception is thrown. Now, the Java versions on the two machines are slightly different. Both the machines have Sun's java, the Linux machine has 1.6.0_10, while the Windows machine has 1.6.0_08, or maybe 07 or 06, I can't remember the exact number right now, and don't have the machine at hand. But even though the minor versions of the Javas are slightly different, the code shouldn't break like this. Does anyone understand what's wrong here?