I just wanted to notify that there seems to be a problem with multiple jars in one rar file. According to JCA 1.0, this is allowed, but JBoss (3.0.4) yields an error.
You have to repackage the jars into one or include them in unpacked (i.e. class files) form.
Could you please file a bug report showing the structure of the failing .rar? If you are using any manifest classpath entries please show them as well.