ORA-01122 database file string failed verification check
Cause: The information in this file is inconsistent with information from the control file. See accompanying message for reason.
Action: Make certain that the database files and control files are the correct files for this database.
ORA-01110 data file string: 'string'
Cause: This message reports the file name involved with other messages.
Action: See the associated messages for a description of the problem.
My first thought, therefore, would be to check your control file.
90% of users' problems can be resolved by punching them - the other 10% by switching off their PCs.