When trying to execute a directory, e.g. groovy c:\temp the error message is not very clear: org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, c:\temp: c:\temp (Access is denied) 1 error What it actually should say is: c:\temp is a directory and can not be executed Note that if the patch attached to GROOVY-1596 is not applied, the above results in NPE.