Debugging server-side scripts in the Metastorm BPM can be difficult. One thing that can help with debugging JScript/VBscript scripts is the FreeFlow Administrator. When an error occurs in your script, generally you’ll be given a line number where the error occurred. This may not relate to a line number in the Designer because scripts are merged together when they get published to the database. The FreeFlow Administrator provides a simple way to view your scripts and see the line numbers and hence track down bugs more easily.
Unfortunately in the world of JScript.NET, when an error occurs you won’t get a line number telling you where it happened. If you want to learn more about debugging .NET code in Metastorm BPM, I would recommend Process Mapping’s .NET course (generally presented by myself).