System.Data.SQLite.SQLiteException (0x80004005): file is encrypted or is not a databasefile is encrypted or is not a database
   en System.Data.SQLite.SQLite3.Prepare(SQLiteConnection cnn, String strSql, SQLiteStatement previous, UInt32 timeoutMS, String& strRemain)
   en System.Data.SQLite.SQLiteCommand.BuildNextCommand()
   en System.Data.SQLite.SQLiteCommand.GetStatement(Int32 index)
   en System.Data.SQLite.SQLiteDataReader.NextResult()
   en System.Data.SQLite.SQLiteDataReader…ctor(SQLiteCommand cmd, CommandBehavior behave)
   en System.Data.SQLite.SQLiteCommand.ExecuteReader(CommandBehavior behavior)
   en System.Data.SQLite.SQLiteCommand.ExecuteNonQuery()
   en System.Data.SQLite.SQLiteConnection.Open()
   en MailClient.Storage.Data.DataStore.GetConnection(String relativeName)
   en DbRepair.CorruptionChecker.CheckCorruption()
   en DbRepair.FormCheck.Check(Object state)

Hello Talleres,
seems like something altered your database or the program is looking for a database at incorrect location.
Have you changed any setting?
Is there any security software that could have altered these files?

Try restarting your device and try again.
If this does not help, you might have to start over with a clean database.
You will need to dleete the previous database files (default location: C:\Users%windows user account%\AppData\Roaming\eM Client) and then open eM Client and either start over or restore from a backup.