Run the following SQL commands for the library/file involved. You will need to use command STRSQL, press Enter, paste in the command, change the library and file parameters to your values and press enter. Then go back in to SFE and try to edit the file.
DELETE FROM PSSECURE/DBW04P WHERE W4LIB = 'LibraryinError' and W4FILE = 'FileinError'
DELETE FROM PSSECURE/DBW90P WHERE W9LIB = 'LibraryinError' and W9FILE = 'FileinError'
DELETE FROM PSSECURE/DBW02P WHERE APLIB = 'LibraryinError' and APFILE = 'FileinError'
Another option is to clear the three files if you encounter the same symptoms for other files. They will be repopulated the next time you use SFE for the library/file.
Files can be corrupted during product upgrade.