while upgrading to CMS5 you need to convert your Forms to XForms. But trying to do so, I encountered an error. It dies a bit after the EPiServer.Admin.ConvertFormToXform.ConvertForm2Xform method and its during System.Xml.XmlTextReaderImpl.ParseQName. The problem was that some of the fields started off with an integer. That is ”1. question” and so on. Simply changing the names of the fields to something else like ”Question 1” was enough to make it work.
Not the prettiest fix, but it will do the job