I created a model using material 21 User Defined. I later created a new material in the materials toolbox. Now when I try to use my new material in my old model I get the following error.

"Error occurred during number read - please reenter value"

This material works in my other models. What am I missing here?

Does this error happen when you "select" your new material from the "Drop List", or does it happen when you manually type in the material number?

If it happens when you type in the material number, go back to the Material Database Editor and make sure you added an "All Codes" entry for the new material, not just the single entry for the Piping Code you're interested in.