When opening an existing WaterGEMS or WaterCAD V8i SELECTseries 3 model, error messages are generated. If the model is opened in SELECTseries 3, the error says "Operation invalid without a current index". If the model is opened in SELECTseries 4, the error says "Error in the application".
This is likely due to a corruption in the database file. There are a couple of things that you can try.
If you have WaterGEMS or WaterCAD V8i SELECTseries 3 or 4 installed, open the program, but do not open a model file. Next, go to Tools > Database Utilities > Compact Database and select the database file. Next, choose the selection to purge the database to save space. Once that is completed, try opening the model to see if that helps.
If that doesn't help, try moving just the .wtg and .wtg.mdb files to a new folder location. At times, one of the supporting files can cause an issue when opening a model. Open the model from the new file location and see if the error occurs.
For SELECTseries 4, it would be the .wtg and .wtg.sqlite files.
If the issue still occurs, see if you have a recent archived copy or a recent backup database file. The backup files will have file extensions similar to ".wtg.mdb.01.bak". You can rename the backup to "wtg.mdb" and import the database into a new worksheet.
For SELECTseries 4, it would be .wtg.SQLite.01.bak.
If you do not have a backup or archived copy of the database, please contact Bentley Technical Support for further assistance.