I first thought you were running from a SVN checkout.
If you are using the M4 download, then it looks like the pom.xml doesn't include the milestone repository.
You need to add the following to the pom.xml under the <repository> entry found at line 197:
Code:
<repository>
<id>com.springsource.repository.bundles.milestone</id>
<name>SpringSource Enterprise Bundle Repository -
SpringSource Bundle Milestones</name>
<url>http://repository.springsource.com/maven/bundles/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>