Also had problems with upload : I had to replace many ActionRequest by UploadPortletRequest, and using method
 addXXX(ActionRequest actionRequest, ActionResponse response) throws Exception {
        UploadPortletRequest request = PortalUtil.getUploadPortletRequest(actionRequest);

actionRequest is used only in PortalUtil.copyRequestParameters(actionRequest, response);
Add to get rid of apache's FileItem, and using Liferay's.
(I use Liferay 6.1EE GA2)