Looks like i have the same problem. We wrote quite big application based on Cocoon 2, and running it on JBoss 2.4.3 is about 3 times faster that on JBoss 3.0.2.
Optimization software indicates that most of the time is spent in java.net.URLClassLoader which is used by org.jboss.mx.loading.UnifiedClassLoader.getResource() method. The last one method is used by xalan and xpath.
This issue blocks our project from moving to jboss 3 and running it on the cluster.
Someone can explain why it happens and if can we expect fixing of this problem?
in a way it is good to know that I am not the only one with this problem.
I reply only to say that I have reposted the question in the 'Installation & Configuration' forum (with the same subject as here). A JBoss developer has reacted, but only to say to try a newer JBoss so far. Anyway, sorry about the crossposting, but maybe it is better to discuss the topic further there (I reposted because there seem to be more eyes watching in that forum).