Erro ao iniciar Tomcat 7

BOm, depois que coloquei a biblioteca primefaces.3.5.jar dentro de WEB-INF/lib ocorreu o seguinte erro no meu tomcat:

SEVERE: Critical error during deployment: 
com.sun.faces.config.ConfigurationException: 
  Source Document: jar:file:/C:/Users/Ronaldo/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/ApplicationJSF2/WEB-INF/lib/primefaces-3.5.jar!/META-INF/faces-config.xml
  Cause: Class 'org.primefaces.component.fileupload.FileUploadRenderer' is missing a runtime dependency: java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileItem
	at com.sun.faces.config.processor.AbstractConfigProcessor.createInstance(AbstractConfigProcessor.java:339)
	at com.sun.faces.config.processor.RenderKitConfigProcessor.addRenderers(RenderKitConfigProcessor.java:313)
	at com.sun.faces.config.processor.RenderKitConfigProcessor.process(RenderKitConfigProcessor.java:179)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ManagedBeanConfigProcessor.process(ManagedBeanConfigProcessor.java:270)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ValidatorConfigProcessor.process(ValidatorConfigProcessor.java:120)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ConverterConfigProcessor.process(ConverterConfigProcessor.java:126)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ComponentConfigProcessor.process(ComponentConfigProcessor.java:117)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ApplicationConfigProcessor.process(ApplicationConfigProcessor.java:340)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.LifecycleConfigProcessor.process(LifecycleConfigProcessor.java:116)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.FactoryConfigProcessor.process(FactoryConfigProcessor.java:239)
	at com.sun.faces.config.ConfigManager.initialize(ConfigManager.java:435)
	at com.sun.faces.config.ConfigureListener.contextInitialized(ConfigureListener.java:214)
	at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4701)
	at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5204)
	at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5199)
	at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
	at java.util.concurrent.FutureTask.run(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileItem
	at java.lang.Class.getDeclaredMethods0(Native Method)
	at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
	at java.lang.Class.getDeclaredMethods(Unknown Source)
	at com.sun.faces.util.Util.classHasAnnotations(Util.java:976)
	at com.sun.faces.application.ApplicationInstanceFactoryMetadataMap.onPut(ApplicationInstanceFactoryMetadataMap.java:75)
	at com.sun.faces.application.ApplicationInstanceFactoryMetadataMap.onPut(ApplicationInstanceFactoryMetadataMap.java:43)
	at com.sun.faces.util.MetadataWrapperMap.put(MetadataWrapperMap.java:91)
	at com.sun.faces.config.processor.AbstractConfigProcessor.loadClass(AbstractConfigProcessor.java:378)
	at com.sun.faces.config.processor.AbstractConfigProcessor.createInstance(AbstractConfigProcessor.java:278)
	... 26 more
Caused by: java.lang.ClassNotFoundException: org.apache.commons.fileupload.FileItem
	at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1676)
	at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1521)
	... 35 more

Jul 19, 2013 8:24:43 PM org.apache.catalina.core.StandardContext listenerStart
SEVERE: Exception sending context initialized event to listener instance of class com.sun.faces.config.ConfigureListener
java.lang.RuntimeException: com.sun.faces.config.ConfigurationException: 
  Source Document: jar:file:/C:/Users/Ronaldo/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/ApplicationJSF2/WEB-INF/lib/primefaces-3.5.jar!/META-INF/faces-config.xml
  Cause: Class 'org.primefaces.component.fileupload.FileUploadRenderer' is missing a runtime dependency: java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileItem
	at com.sun.faces.config.ConfigureListener.contextInitialized(ConfigureListener.java:273)
	at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4701)
	at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5204)
	at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5199)
	at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
	at java.util.concurrent.FutureTask.run(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: com.sun.faces.config.ConfigurationException: 
  Source Document: jar:file:/C:/Users/Ronaldo/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/ApplicationJSF2/WEB-INF/lib/primefaces-3.5.jar!/META-INF/faces-config.xml
  Cause: Class 'org.primefaces.component.fileupload.FileUploadRenderer' is missing a runtime dependency: java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileItem
	at com.sun.faces.config.processor.AbstractConfigProcessor.createInstance(AbstractConfigProcessor.java:339)
	at com.sun.faces.config.processor.RenderKitConfigProcessor.addRenderers(RenderKitConfigProcessor.java:313)
	at com.sun.faces.config.processor.RenderKitConfigProcessor.process(RenderKitConfigProcessor.java:179)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ManagedBeanConfigProcessor.process(ManagedBeanConfigProcessor.java:270)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ValidatorConfigProcessor.process(ValidatorConfigProcessor.java:120)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ConverterConfigProcessor.process(ConverterConfigProcessor.java:126)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ComponentConfigProcessor.process(ComponentConfigProcessor.java:117)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.ApplicationConfigProcessor.process(ApplicationConfigProcessor.java:340)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.LifecycleConfigProcessor.process(LifecycleConfigProcessor.java:116)
	at com.sun.faces.config.processor.AbstractConfigProcessor.invokeNext(AbstractConfigProcessor.java:152)
	at com.sun.faces.config.processor.FactoryConfigProcessor.process(FactoryConfigProcessor.java:239)
	at com.sun.faces.config.ConfigManager.initialize(ConfigManager.java:435)
	at com.sun.faces.config.ConfigureListener.contextInitialized(ConfigureListener.java:214)
	... 8 more

Fácil, você não colocou o jar commons-fileupload na pasta lib da tua aplicação.
Se usa maven, não incluiu a dependência da commons-fileupload no pom.xml.

Resolvido.