We are using JIRA 4.1.2 and have been doing so for over a year and a half. This problem has never surfaced until now. Many fields (some of which are required) are no longer showing up on the create screen, edit screen and the screens that follow. When you go into the Custom fields area the fields show up and when you go the field Configuration schemes for the fields they are associated with the screens but when you try to create an issue the fields are no longer present. There are a few admins but it appears none have made any configuration changes today (the system was working earlier today with no issues).