I have a Groovy script that is failing to download its Grape dependencies.  I believe I've set my proxy correctly, and I also tried outside of our firewall, and got the same error.

This is the beginning of my script:
---------------------
#! /usr/bin/env groovy
@Grapes([
	@Grab("org.codehaus.geb:geb-core:0.7.0"),
	@Grab("org.seleniumhq.selenium:selenium-htmlunit-driver:2.23.1"),
	@Grab("org.seleniumhq.selenium:selenium-support:2.23.1")
	])
import geb.Browser;
...
------------------

When I run this (Groovy Version: 2.4.3 JVM: 1.7.0_51 Vendor: Oracle Corporation OS: Windows 7), I get the following:
---------------
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
General error during conversion: Error grabbing Grapes -- [download failed: com.google.guava#guava;12.0!guava.jar, download failed: com.google.code.findbugs#jsr305;1.3.9!jsr305.jar, download failed: xml-apis#xml-apis;1.3.04!xml-apis.jar, download failed: commons-collections#commons-collections;3.2.1!commons-collections.jar, download failed: commons-lang#commons-lang;2.6!commons-lang.jar, download failed: commons-logging#commons-logging;1.1.1!commons-logging.jar]

java.lang.RuntimeException: Error grabbing Grapes -- [download failed: com.google.guava#guava;12.0!guava.jar, download failed: com.google.code.findbugs#jsr305;1.3.9!jsr305.jar, download failed: xml-apis#xml-apis;1.3.04!xml-apis.jar, download failed: commons-collections#commons-collections;3.2.1!commons-collections.jar, download failed: commons-lang#commons-lang;2.6!commons-lang.jar, download failed: commons-logging#commons-logging;1.1.1!commons-logging.jar]
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at org.codehaus.groovy.reflection.CachedConstructor.invoke(CachedConstructor.java:77)
	at org.codehaus.groovy.reflection.CachedConstructor.doConstructorInvoke(CachedConstructor.java:71)
	at org.codehaus.groovy.runtime.callsite.ConstructorSite$ConstructorSiteNoUnwrap.callConstructor(ConstructorSite.java:81)
	at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallConstructor(CallSiteArray.java:57)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:232)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:244)
	at groovy.grape.GrapeIvy.getDependencies(GrapeIvy.groovy:418)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
---------------------

What might be going on here?