We have a war file that is using SLF4J and Logback Classic/Core 0.9.29, running in WebLogic 11. Any thoughts to why I would get a no class found even though the jar exists? I assume we have jars in the war that are causing conflicts. Thanks...jay Exception in thread "ListenerContainer-1" java.lang.NoClassDefFoundError: ch/qos/logback/classic/spi/ThrowableProxy at ch.qos.logback.classic.spi.LoggingEvent.<init>(LoggingEvent.java:123) at ch.qos.logback.classic.Logger.buildLoggingEventAndAppend(Logger.java:471) at ch.qos.logback.classic.Logger.filterAndLog_0_Or3Plus(Logger.java:427) at ch.qos.logback.classic.Logger.log(Logger.java:846) at org.apache.commons.logging.impl.SLF4JLocationAwareLog.warn(SLF4JLocationAwareLog.java:199) at org.springframework.jms.listener.DefaultMessageListenerContainer.handleListenerSetupFailure(DefaultMessageListenerContainer.java:818) at org.springframework.jms.listener.DefaultMessageListenerContainer$AsyncMessageListenerInvoker.run(DefaultMessageListenerContainer.java:968) at java.lang.Thread.run(Thread.java:619) -- View this message in context: http://old.nabble.com/NoClassDefFoundError%3A-ch-qos-logback-classic-spi-Thr... Sent from the Logback User mailing list archive at Nabble.com.