About the only thing that may cause an error when you run one of the actions is the use of a "Place" command within the action.
A Place command is used to take the contents of one file and "place" it into the current document. In the case of Greeting Cards, the Place command is used to include the signature block on the back of the cards. With Calendars, the Place command is used to lay out the calendar grid and dates.
The most common error is when the Place command is not available. This means that Photoshop is not able to find the file that is being placed.
The file that may be generating the Place command error depends upon what program you are running at the time. Follow the links below for details about each set of actions.