I am using an object File that inherits from System.FileDocument where I can upload a document and give it a version number. This and the downloading works fine but when I want to edit an existing file, change it and save it, it says: A server exception occured: Change object should not be null. I tried splitting my form from NewEdit into a separate New and Edit form and removing the actual FileUploader from the Edit form but seems this was not the problem.