When importing an older model file into WaterCAD or WaterGEMS, the following error message is generated:
"Object reference not set to an instance of an object"
"The path provided is not a WaterCAD V7 file"
Option 1 - Use a backup model
The database associated with the model could have become corrupted. If you have a backup file or an older version of the model file, try to open this instead.
See: Can I restore a backup file of my model project or software component?
Option 2 - Compact the .MDB database in Microsoft Access
Issues with a .MDB database file can sometimes be corrected by compacting that file in Microsoft Access. If the file opens in Microsoft Access, then try to compact the database. If the file will not open in Access, the file is corrupted and cannot be used. You can try to recreate the file in WaterCAD or WaterGEMS. If you have a source file for the model, such as a Shapefile, ModelBuilder is a good tool for this.
Option 3 - Upgrade
It may help to download and install the latest version of the product and patch set.
[Defect Reference # 803172]
Converting older WaterCAD/WaterGEMS files into WaterCAD/WaterGEMS V8i format and saving presentation settings