Spurious (?) warnings about "More then one reference to the same implementation was found for org.jboss.arquillian.spi.ApplicationArchiveGenerator, please verify you classpath"

In our Arquillian+RSpec (JRuby) integration, everything works, but we repeatedly get this warning:

[WARNING] Feb 8, 2011 10:46:57 AM org.jboss.arquillian.impl.DynamicServiceLoader verifySameImplementation
[WARNING] WARNING: More then one reference to the same implementation was found for org.jboss.arquillian.spi.ApplicationArchiveGenerator, please verify you classpath

Would be lovely to have one of:

• Instructions on how to solve the root cause (which classpath? I think we have 3: maven's, jruby's and AS's...)
• Instructions on how to mute the warning