i have this error with mvn clean package

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.1:compile (default-compile) on project forge-shell-api: Compilation failure
[ERROR] /home/fiorenzo/git/core/shell-api/src/main/java/org/jboss/forge/shell/util/ResourceUtil.java:[111,23] invalid inferred types for R; inferred type does not conform to declared bound(s)
[ERROR] inferred: java.util.Collection<E>
[ERROR] bound(s): java.util.Collection<org.jboss.forge.resources.Resource<?>>
[ERROR] -> [Help 1]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR]   mvn <goals> -rf :forge-shell-api

[ubuntu 12.04 - Apache Maven 3.0.4 - Java version: 1.6.0_24, vendor: Sun Microsystems Inc. Java home: /usr/lib/jvm/java-6-openjdk-amd64/jre Default locale: it_IT, platform encoding: UTF-8 OS name: "linux", version: "3.2.0-29-generic", arch: "amd64", family: "unix"]

Any help on this?