maven-dependency-plugin:unpack-dependencies doesn't always work

[EJ Ciramella]

I'm having a bit of difficulty with unpacking some dependencies - and I'm not 
entirely sure why this process is failing.

In _some_ projects, we define the dependency we'd like to unpack within the 
plugin configuration - like this:

         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-dependency-plugin</artifactId>
           <version>2.1</version>
           <dependencies>
              <dependency>
                  <groupId> </groupId>
                  <artifactId> </artifactId>
                  <version></version>
                  <classifier>templates</classifier>
                  <scope>provided</scope>
                  <type>zip</type>
              </dependency>
           </dependencies>
           <executions>
              <execution>
                  <id>unpack- templates</id>
                  <phase>generate-resources</phase>
                  <goals>
                      <goal>unpack-dependencies</goal>
                  </goals>
                  <configuration>
                      <overWriteReleases>false</overWriteReleases>
                      <overWriteSnapshots>true</overWriteSnapshots>
                      <includeGroupIds> </includeGroupIds>
                      <includeArtifactIds> </includeArtifactIds>
                      <classifier>templates</classifier>
                      <type>zip</type>
                      <outputDirectory>target/foo</outputDirectory>
                  </configuration>
              </execution>
           </executions>
         </plugin>

In another project, if I copy and paste this block in, it not only doesn't 
unpack, but doesn't fail.  With -X -e, the debug output shows it saying "hey, 
I'm unpacking now" but there's nothing there.

Any suggestions?