Error in GMaven Plugin

Question

Whenever I execute the gmaven plugin, I get the following problem

org.apache.maven.lifecycle.LifecycleExecutionException: Internal error in the plugin manager executing goal 'org.codehaus.groovy.maven:gmaven-plugin:1.0-rc-5:generateStubs': Mojo execution failed.

The relevant section of my POM is below. Any thoughts why?

<plugin>
    <groupId>org.codehaus.groovy.maven</groupId>
    <artifactId>gmaven-plugin</artifactId>
    <version>1.0-rc-5</version>
    <executions>
        <execution>
            <goals>
                <goal>generateStubs</goal>
                <goal>compile</goal>
                <goal>generateTestStubs</goal>
                <goal>testCompile</goal>
            </goals>
            <configuration>
                <sources>
                    <fileset>
                        <directory>${project.build.sourceDirectory}</directory>
                        <includes>
                            <include>**/*.groovy</include>
                        </includes>
                        <directory>${project.build.testDirectory}</directory>
                        <includes>
                            <include>**/*.groovy</include>
                        </includes>
                    </fileset>
                </sources>
            </configuration>
        </execution>
    </executions>
</plugin>

Answer 1

Are you sure there is no formatting issue with the POM (either in this section or in another section of your POM)?
See this bug for more details, also reported here.

Answer 2

It turned out to be a mismatch with my groovy libraries and gmaven versions. I cleared out my local repository and updated to the latest versions. Now all is back to normal.