I presume this is the stack trace you mean.
java.lang.StackOverflowError
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:206)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
at org.codehaus.groovy.eclipse.refactoring.actions.OrganizeGroovyImports$FindUnresolvedReferencesVisitor.handleType(OrganizeGroovyImports.java:253)
On a related note: If this enum is in a package, the syntax highlighting had troubles with the word 'package' (a blue italic p), and the keyword 'enum' was not recognized at all.