Helped a user with this issue this morning. User was logged in and attempting to execute tests and the "Failed to Copy Design Steps" error was produced and the run is discontinued.
I removed him from the project, re-added him to the project and he was then able to execute test runs.
Our assumption is that there is a reference point in the temp directory that has become corrupted at some point and when the user is recreated in the project, all the workflow is also recreated along with any table pointers etc.
I have attached a txt file of the full error description for those that would like to investigate further.
While I have been working for Businesses that are Vendor partners with HP, IBM and Microsoft, my opinions and advice is my own.
The solutions provided are either sourced from my own scripting libraries or from a quick Google Search.