First off, upgrade those servers' Service packs to 6a, that will help you with a few things. Next, try turning off the printers, and canceling the job from the originating workstaion. If that does not work, then go into services in control panel, and recycle your spooler service, and that will kill it. I have had that very same problem with many HP color printers ESPECIALLY the 2000, and 2500 series. These are a few suggestions, try them, and let me know if they work, if not I have some other stuff for you to try.
Good Luck,
SteelDragon