When a long script is pasted into the JellyRunner it takes a long time to execute this script. Often JellyRunner will return with an error "Could not execute script.". The JellyRunner has run only about halfway through the script at this point and there's nothing special about the following tags. In fact these execute correctly if executed separately in a new JellyRunner.

The extra information provided by the JellyRunner:

Error: <JiraJelly xmlns:jira="jelly:com.atlassian.jira.jelly.JiraTagLib">
Exception: org.apache.commons.jelly.JellyTagException: null:138:0: java.lang.NullPointerException
java.io.PrintWriter@412d02