Simple Problem with exec plugin

[Tim Patton]

I'm trying to get the exec plugin to work, since maven seems like it would make 
a great application launcher and save me time editing my 1000 char classpath.

I have this in my pom.xml for a project consisting of several modules:

<build>
..
<plugin>
        <groupId>org.codehaus.mojo</groupId>
      <artifactId>exec-maven-plugin</artifactId>
      <version>1.0.1</version>
      <configuration>
          <mainClass>dealcatcher.kolinka.profiler.SingleForumProfile</mainClass>
      </configuration>
      </plugin>
..
</build>

When I run it with "mvn exec:java" I get "Could not load main class.  
Terminating.".  I try running mvn package or mvn install beforehand but I'm not 
sure what I am missing to make this work.

Tim