Dexei só o input file e o problema continua 
Log sem arquivo:
11:38:05,404 DEBUG VRaptor:81 - VRaptor received a new request
11:38:05,405 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor ResourceLookupInterceptor
11:38:05,405 DEBUG DefaultResourceTranslator:51 - trying to access /imagem/gravar
11:38:05,406 DEBUG DefaultResourceTranslator:61 - found resource [DefaultResourceMethod: ImagemController.gravarImagemController.gravar(Imagem, UploadedFile)]
11:38:05,406 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor HibernateTransactionInterceptor
11:38:05,412 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor ExceptionHandlerInterceptor
11:38:05,412 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor CommonsUploadMultipartInterceptor
11:38:05,412 INFO CommonsUploadMultipartInterceptor:93 - Request contains multipart data. Try to parse with commons-upload.
11:38:05,413 DEBUG CommonsUploadMultipartInterceptor:175 - Using repository /var/folders/QW/QWzSirLAGCiCI8EsqMbCgU+++TI/-Tmp- for file upload
11:38:05,413 DEBUG CommonsUploadMultipartInterceptor:102 - Found 1 attributes in the multipart form submission. Parsing them.
11:38:05,414 DEBUG CommonsUploadMultipartInterceptor:119 - A file field was empty: arquivoImagem
11:38:05,414 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor FlashInterceptor
11:38:05,414 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor InstantiateInterceptor
11:38:05,414 DEBUG IogiParametersProvider:56 - IogiParametersProvider is up
11:38:05,415 DEBUG LazyInterceptorHandler:58 - Invoking interceptor ParametersInstantiatorInterceptor
11:38:05,415 DEBUG ParanamerNameProvider:51 - Found parameter names with paranamer for ImagemController.gravar(Imagem, UploadedFile) as [imagem, arquivoImagem]
11:38:05,416 DEBUG IogiParametersProvider:69 - getParametersFor() called with parameters Parameters() and targets [Target(name=imagem, type=class br.com.pagina.modelo.Imagem), Target(name=arquivoImagem, type=interface br.com.caelum.vraptor.interceptor.multipart.UploadedFile)].
11:38:05,416 DEBUG ParanamerNameProvider:51 - Found parameter names with paranamer for Imagem() as []
11:38:05,417 WARN UploadedFileConverter:51 - There was an error when uploading the file {}. Please verify if commons-fileupload jars are in your classpath or you are using a Servlet 3 Container.
11:38:05,418 DEBUG ParametersInstantiatorInterceptor:88 - There are conversion errors: [ValidationMessage{category=arquivoImagem, message=Invalid upload, parameters=null}]
11:38:05,419 DEBUG ParametersInstantiatorInterceptor:90 - Parameter values for [DefaultResourceMethod: ImagemController.gravarImagemController.gravar(Imagem, UploadedFile)] are [br.com.pagina.modelo.Imagem@1786b2ca, null]
11:38:05,419 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor ExecuteMethodInterceptor
11:38:05,419 DEBUG ExecuteMethodInterceptor:60 - Invoking ImagemController.gravar(Imagem, UploadedFile)
11:38:05,420 DEBUG ParanamerNameProvider:51 - Found parameter names with paranamer for ImagemController.gravar(Imagem, UploadedFile) as [imagem, arquivoImagem]
11:38:05,421 DEBUG CglibProxifier:74 - a proxy for interface br.com.caelum.vraptor.view.LogicResult is created as class br.com.caelum.vraptor.view.LogicResult$$EnhancerByCGLIB$$4e58f788
11:38:05,422 DEBUG DefaultLogicResult:123 - redirecting to class ImagemController
11:38:05,422 DEBUG CglibProxifier:74 - a proxy for class br.com.pagina.controller.ImagemController is created as class br.com.pagina.controller.ImagemController$$EnhancerByCGLIB$$b0cbe213
11:38:05,423 DEBUG CglibProxifier:74 - a proxy for class br.com.pagina.controller.ImagemController is created as class br.com.pagina.controller.ImagemController$$EnhancerByCGLIB$$b0cbe213
11:38:05,424 DEBUG DefaultLogicResult:138 - redirecting to /pagina/imagem/nova
11:38:05,426 DEBUG VRaptor:95 - VRaptor ended the request
log informando um arquivo:
11:42:50,124 DEBUG VRaptor:81 - VRaptor received a new request
11:42:50,165 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor ResourceLookupInterceptor
11:42:50,166 DEBUG DefaultResourceTranslator:51 - trying to access /imagem/gravar
11:42:50,166 DEBUG DefaultResourceTranslator:61 - found resource [DefaultResourceMethod: ImagemController.gravarImagemController.gravar(Imagem, UploadedFile)]
11:42:50,167 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor HibernateTransactionInterceptor
11:42:50,170 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor ExceptionHandlerInterceptor
11:42:50,170 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor CommonsUploadMultipartInterceptor
11:42:50,170 INFO CommonsUploadMultipartInterceptor:93 - Request contains multipart data. Try to parse with commons-upload.
11:42:50,171 DEBUG CommonsUploadMultipartInterceptor:175 - Using repository /var/folders/QW/QWzSirLAGCiCI8EsqMbCgU+++TI/-Tmp- for file upload
11:42:50,172 DEBUG CommonsUploadMultipartInterceptor:102 - Found 1 attributes in the multipart form submission. Parsing them.
11:42:50,173 DEBUG CommonsUploadMultipartInterceptor:115 - arquivoImagem is a file
11:42:50,224 DEBUG VRaptorRequest:86 - Setting arquivoImagem with [arquivoImagem]
11:42:50,225 DEBUG CommonsUploadMultipartInterceptor:165 - Uploaded file: arquivoImagem with [uploadedFile uploadedCompleteName=Lagaffe.gif uploadedName=Lagaffe.gif contentType=image/gif]
11:42:50,225 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor FlashInterceptor
11:42:50,225 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor InstantiateInterceptor
11:42:50,226 DEBUG IogiParametersProvider:56 - IogiParametersProvider is up
11:42:50,226 DEBUG LazyInterceptorHandler:58 - Invoking interceptor ParametersInstantiatorInterceptor
11:42:50,227 DEBUG ParanamerNameProvider:51 - Found parameter names with paranamer for ImagemController.gravar(Imagem, UploadedFile) as [imagem, arquivoImagem]
11:42:50,227 DEBUG IogiParametersProvider:69 - getParametersFor() called with parameters Parameters(Parameter(arquivoImagem -> arquivoImagem)) and targets [Target(name=imagem, type=class br.com.pagina.modelo.Imagem), Target(name=arquivoImagem, type=interface br.com.caelum.vraptor.interceptor.multipart.UploadedFile)].
11:42:50,228 DEBUG ParanamerNameProvider:51 - Found parameter names with paranamer for Imagem() as []
11:42:50,238 DEBUG ParametersInstantiatorInterceptor:90 - Parameter values for [DefaultResourceMethod: ImagemController.gravarImagemController.gravar(Imagem, UploadedFile)] are [br.com.pagina.modelo.Imagem@1d2fa9ae, [uploadedFile uploadedCompleteName=Lagaffe.gif uploadedName=Lagaffe.gif contentType=image/gif]]
11:42:50,239 DEBUG ToInstantiateInterceptorHandler:53 - Invoking interceptor ExecuteMethodInterceptor
11:42:50,239 DEBUG ExecuteMethodInterceptor:60 - Invoking ImagemController.gravar(Imagem, UploadedFile)
11:42:54,806 DEBUG CglibProxifier:74 - a proxy for interface br.com.caelum.vraptor.view.LogicResult is created as class br.com.caelum.vraptor.view.LogicResult$$EnhancerByCGLIB$$4e58f788
11:42:54,812 DEBUG CglibProxifier:74 - a proxy for class br.com.pagina.controller.ImagemController is created as class br.com.pagina.controller.ImagemController$$EnhancerByCGLIB$$b0cbe213