Maven and scala:doc

[dacanalr]

Hi,
the commands mvn scala:doc throws this exception :

java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:
39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:
25)
at java.lang.reflect.Method.invoke(Method.java:597)
at
org_scala_tools_maven_executions.MainHelper.runMain(MainHelper.java:
161)
at
org_scala_tools_maven_executions.MainWithArgsInFile.main(MainWithArgsInFile.java:
26)
Caused by: java.lang.NoClassDefFoundError: scala/runtime/BoxedArray
at org.scala_tools.vscaladoc.Main.main(Main.scala)
... 6 more
Caused by: java.lang.ClassNotFoundException: scala.runtime.BoxedArray
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 7 more

How can i solve it ?

PS : here you some info from the pom file :

<properties>
<scala.version>2.8.1</scala.version>
<!-- Common plugin settings -->
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>${project.build.sourceEncoding}</
project.reporting.outputEncoding>
<!-- vscaladoc settings -->
<maven.scaladoc.vscaladocVersion>1.2-m1</
maven.scaladoc.vscaladocVersion>
<vscaladoc.links.liftweb.pathsufix>scaladocs/</
vscaladoc.links.liftweb.pathsufix>
<vscaladoc.links.liftweb.baseurl>http://scala-tools.org/mvnsites/
liftweb</vscaladoc.links.liftweb.baseurl>
</properties>

Thanks in advance !!