Error occurs when using some commands.

Autodesk has released AutoCAD 2025.1.4 & 2026.1.2 updates which breaks HydraCAD. It includes a major programming change by Autodesk that will require a lot of work and a large update by us. That update is being worked on right now, along with a version of HydraCAD for AutoCAD 2027. All are now affected by essentially the same programming change.

BinaryFormatter serialization and deserialization are disabled within this application. See  https://aka.ms/binaryformatter for more information.

Other commands with this error;

Sprinkler Layout dialog (SL command)

Default Dialog Location (DDL command)

When clicking the abacus to enter a length, you get this error;

Unhandled exception has occurred in a component in your application.  If you click Continue, the application will ignore this error and attempt to continue.

Index and length must refer to a location within the string.  Parameter name: length