The aggregator underwent an overhaul recently. If you can, download the CP branch and try that. If you're already using that code, post back here.
JBESB_4_2_1_GA_CP_IR5 works perfectly. I noticed you say in a different thread that January will be the JBossAS 4.2.2 compatibility release, would this be rolled up with it?
They'll be released as part of the JBoss SOA Platform. There definitely won't be a community ESB binary available until sometime after that.