It looks like your report template XML file got corrupted; you would need to delete it. Close all instances of CAESAR II, then open Windows Explorer and navigate to the CAESAR II installation directory, folder "System", the file name is "C2RPTTMPL.XML" (by default it is "C:\Program Files\COADE\CAESAR II 5.00\System\C2RPTTMPL.XML"). Then start CAESAR II and enter Output Processor -- the default report template file will be created.
This problem can happen if CAESAR II is installed on a shared network drive and several people access it at the same time. In this case it is recommended to implement UserID string in the configuration for each user.