I am using Jetadmin D04.12 on Solaris 2.5/2.5.1 boxes and HP's with virtually the same configuration. The Jetadmin works fine on the SUN's, but not on the HP's. The HP's complain about not being able to get an SNMP request back.
However, the SUN's inetd.conf file is the same as the HP's essentially, and the cables are all fine. I can ping the printer and have double-checked the snmp communities.