Common-loggin exception

Dear Sir : 
my web app sometime happen this exception.
and my webapp will be crash.
my server solution: 
weblogic 7.0
JDK 1.4

Lib:
DBGrid.jar                    jakarta-regexp-1.4.jar
commons-beanutils.jar         jakarta-regexp-1.4.jar.LCK
commons-dbutils-1.1.jar       javamail.jar
commons-digester-1.7.jar      jxl.jar
commons-fileupload-1.1.1.jar  log4j-1.2.13.jar
commons-io-1.2.jar            ognl.jar
commons-lang-2.2.jar          oro-2.0.8.jar
commons-logging.jar           oscore.jar
dwr.jar                       rife-continuations.jar
freemarker.jar                webwork-2.2.4.jar
iTextAsian.jar                xml-apis.jar
itext-1.4.7.jar               xwork.jar

Exception log : 
10:39:15,845 ERROR DispatcherUtils:237 - Could not execute action
org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging
.LogConfigurationException: org.apache.commons.logging.LogConfigurationException
: Invalid class loader hierarchy.  You have more than one version of 'org.apache
.commons.logging.Log' visible, which is not allowed. (Caused by org.apache.commo
ns.logging.LogConfigurationException: Invalid class loader hierarchy.  You have
more than one version of 'org.apache.commons.logging.Log' visible, which is not
allowed.) (Caused by org.apache.commons.logging.LogConfigurationException: org.a
pache.commons.logging.LogConfigurationException: Invalid class loader hierarchy.
  You have more than one version of 'org.apache.commons.logging.Log' visible, wh
ich is not allowed. (Caused by org.apache.commons.logging.LogConfigurationExcept
ion: Invalid class loader hierarchy.  You have more than one version of 'org.apa
che.commons.logging.Log' visible, which is not allowed.))
        at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactory
Impl.java:543)
        at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactory
Impl.java:235)
        at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactory
Impl.java:209)
        at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351)
        at com.opensymphony.xwork.validator.DelegatingValidatorContext$LoggingVa
lidationAware.<init>(DelegatingValidatorContext.java:234)
        at com.opensymphony.xwork.validator.DelegatingValidatorContext.makeValid
ationAware(DelegatingValidatorContext.java:193)
        at com.opensymphony.xwork.validator.DelegatingValidatorContext.<init>(De
legatingValidatorContext.java:53)
        at com.opensymphony.xwork.validator.DefaultActionValidatorManager.valida
te(DefaultActionValidatorManager.java:82)
        at com.opensymphony.xwork.validator.ValidationInterceptor.doBeforeInvoca
tion(ValidationInterceptor.java:109)
        at com.opensymphony.xwork.validator.ValidationInterceptor.doIntercept(Va
lidationInterceptor.java:113)
        at com.opensymphony.xwork.interceptor.MethodFilterInterceptor.intercept(
MethodFilterInterceptor.java:86)
        at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionIn
vocation.java:188)
        at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(Around
Interceptor.java:31)
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