jclouds null pointer exception

.palletservicesvirtualbox.clj

{:vb {:provider "virtualbox"
      :images {:ubuntu-10-10 {:description "Ubuntu 10.10 64bit"
                              :uuid "ea8d17cd-d532-4ce4-82de-d201d773f9d1"
                              :os-family :ubuntu
                              :os-version "10.10"
                              :os-type-id "Ubuntu"
                              :os-64-bit true
                              :sudo-password "superduper"
                              :no-sudo false
                              :username "user"
                              :password "superduper"}}
      :model-path "/Users/blake/.vmfest/models"
      :node-path "/Users/blake/.vmfest/nodes"
      :url "http://localhost:18083"}}

gistfile1.txt

Exception in thread "main" java.lang.NullPointerException
	at java.lang.Class.isAssignableFrom(Native Method)
	at org.jclouds.rest.RestContextSpec.<init>(RestContextSpec.java:60)
	at org.jclouds.rest.RestContextFactory.createContextSpec(RestContextFactory.java:321)
	at org.jclouds.rest.RestContextFactory.createContextBuilder(RestContextFactory.java:234)
	at org.jclouds.compute.ComputeServiceContextFactory.createContext(ComputeServiceContextFactory.java:119)
	at org.jclouds.compute2$compute_service.doInvoke(compute2.clj:91)
	at clojure.lang.RestFn.applyTo(RestFn.java:146)
	at clojure.core$apply.doInvoke(core.clj:608)
	at clojure.lang.RestFn.invoke(RestFn.java:587)
	at pallet.compute.jclouds$eval5008$fn__5010.invoke(jclouds.clj:605)
	at clojure.lang.MultiFn.invoke(MultiFn.java:167)
	at pallet.compute$compute_service.doInvoke(compute.clj:36)
	at clojure.lang.RestFn.applyTo(RestFn.java:139)
	at clojure.core$apply.invoke(core.clj:602)
	at pallet.configure$compute_service_from_map.invoke(configure.clj:166)
	at pallet.configure$compute_service_from_config.invoke(configure.clj:174)
	at pallet.configure$compute_service_from_config_file.doInvoke(configure.clj:196)
	at clojure.lang.RestFn.invoke(RestFn.java:408)
	at pallet.configure$compute_service.invoke(configure.clj:230)
	at clojure.lang.Var.invoke(Var.java:401)
	at clojure.lang.AFn.applyToHelper(AFn.java:161)
	at clojure.lang.Var.applyTo(Var.java:518)
	at clojure.core$apply.invoke(core.clj:600)
	at pallet.compute$service.doInvoke(compute.clj:138)
	at clojure.lang.RestFn.invoke(RestFn.java:408)
	at letterleaf_provision.core$service.invoke(core.clj:10)
	at letterleaf_provision.core$change.invoke(core.clj:37)
	at letterleaf_provision.core$_main.doInvoke(core.clj:49)
	at clojure.lang.RestFn.invoke(RestFn.java:482)
	at clojure.lang.Var.invoke(Var.java:417)
	at user$eval3931.invoke(NO_SOURCE_FILE:1)
	at clojure.lang.Compiler.eval(Compiler.java:6465)
	at clojure.lang.Compiler.eval(Compiler.java:6455)
	at clojure.lang.Compiler.eval(Compiler.java:6431)
	at clojure.core$eval.invoke(core.clj:2795)
	at clojure.main$eval_opt.invoke(main.clj:296)
	at clojure.main$initialize.invoke(main.clj:315)
	at clojure.main$null_opt.invoke(main.clj:348)
	at clojure.main$main.doInvoke(main.clj:426)
	at clojure.lang.RestFn.invoke(RestFn.java:421)
	at clojure.lang.Var.invoke(Var.java:405)
	at clojure.lang.AFn.applyToHelper(AFn.java:163)
	at clojure.lang.Var.applyTo(Var.java:518)
	at clojure.main.main(main.java:37)

repl

letterleaf-provision.core=> (require '[pallet.compute :as compute])
nil
letterleaf-provision.core=> (compute/service :vb)
07:09:33.856 [Thread-2] DEBUG pallet.compute.jclouds - extensions (:slf4j :ssh)
NullPointerException   java.lang.Class.isAssignableFrom (Class.java:-2)