ContentType not applied on folder.Files.Add

Hi,

I have an issue, when i add a file in a Folder the contentType isn't applied.

                        if (fileStream != null)
                        {
                            Hashtable documentMetadata = new Hashtable { 

                                                                            ,{ "vti_title", title }
                                                                            ,{ "ContentTypeId", ReportMetadata.ContentTypeIdValue }
                                                         ,{ "_Author", SPContext.Current.Web.CurrentUser.LoginName}
                                                                   };

                            string fileName = string.Format("{0}.xlsm", reportNumber);
                            using (SPSite site = new SPSite(GEDURL))
                            {
                                using (SPWeb web = site.OpenWeb())
                                {
                                    fileStream.Seek(0, System.IO.SeekOrigin.Begin);

                                    SPFolder spFolder = web.GetFolder(folderUrl);
                                    spFolder.SubFolders[CaseMetadata.TechnicalFolder].Files.Add(fileName, fileStream, documentMetadata, true);

                                }
                            }

                        }

With this version it's working

                        if (fileStream != null)
                        {
                            Hashtable documentMetadata = new Hashtable { 

                                                                            ,{ "vti_title", title }
                                                                            ,{ "ContentTypeId", ReportMetadata.ContentTypeIdValue }
                                                         ,{ "_Author", SPContext.Current.Web.CurrentUser.LoginName}
                                                                   };

                            string fileName = string.Format("{0}.xlsm", reportNumber);
                            using (SPSite site = new SPSite(GEDURL))
                            {
                                using (SPWeb web = site.OpenWeb())
                                {
                                    fileStream.Seek(0, System.IO.SeekOrigin.Begin);

                                    SPFolder spFolder = web.GetFolder(folderUrl);
                                    SPFile file = spFolder.SubFolders[CaseMetadata.TechnicalFolder].Files.Add(fileName, fileStream, documentMetadata, true);

                                    file.Item["ContentTypeId"] = ReportMetadata.ContentTypeIdValue;
                                    file.Item.UpdateOverwriteVersion();
                                }
                            }


                        }

The first code is working perfectly on my devsite but i doesn't work on my production site.

Any idea ?

Regards,

J.D.