I have the same issue using maven 2.2 and eclipse-maven-plugin 2.6 or 2.7 (no problem with 2.5).

My aspectj dependency is 1.6.2

Same problem here, maven 2.1.0, aspectj 1.6.1

(I've had this problem since almost a year, when I started using aspectj and maven)

This is caused by these lines in EclipseClasspathWriter:

// Skip aspectj libraries since they are in the container.
        if ( ( config.getAjdtVersion() != 0 ) && dep.getArtifactId().toLowerCase().indexOf( "aspectj" ) >= 0 )
        {
            return;
        }

It is very annoying it's not possible to add aspectj libraries to the classpath. Somehow my JUnit-Spring tests work fine with Maven but in Rad they don't run because the aspectj-weaver classes are not found. And these lines prevent my from adding the required dependencies to the Eclipse classpath.

Any ideas how to workaround this? What do they mean by "Skip aspectj libraries since they are in the container." ? In which container? We're using the WebSphere JRE and WebSphere Application Service libraries for our projects, but these don't have aspectj in them.

You can set <ajdtVersion>none</ajdtVersion> in your eclipse plugin config. By default the plugin supposes you have, and you are using AJDT plugin if you aspectj dependencies in your project.
I'll change this behavior to set ajdtVersion to none by default in 2.8

Agreed, this is an annoying bug. I upgrade my AspectJ libraries faster than Eclipse.

fixed by MECLIPSE-594