hmmm, this didn't seem to have anything to do with it. I added jaxen jar file, but the error persisted. (I guess this one is already included in the seam/jboss libs, no?). As I mentioned before, the error occurred after a file was uploaded, and not processed. Adding this to my stateful session bean fixed the problem: | if (this.newUploadFile!=null) { | try { | this.newUploadFile.close(); | this.newUploadFile = null; | } | catch (Exception e) { | } | } | I guess I'm not the only one having this problem (InputStream doesn't seem to be serializable), since I'm using straightforward elements (s:fileUpload to an inputstream). Perhaps it can be included/mentioned in the docs? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4105632#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...