The following error was being emitted by the resources plugin using Maven 2.2.0:

[INFO] [resources:testResources {execution: default-testResources}]
[WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent!

This warning is a hint to update your pom with an encoding to be used. For example:

<project>
  ...
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    ...
  </properties>
  ...
</project>

This setting is applied across all plugins (in builds of Maven prior to 2.1.0 encoding was required to be set on a per plugin basis).

More details are available here: http://docs.codehaus.org/display/MAVENUSER/POM+Element+for+Source+File+Encoding.