The kernel only sees it as usb
I think that's my problem. The kernel doesn't see anything when I plug my HP laserjet 4Mplus into the usb port. Nor does it see my HP laserjet 6MP. Tried different cables. If it would see it, I could configure it. As it is, I have to use the parallel port, which is kind of slow.
What I meant, is the kernel is supposed to only care if it USB in the case of printers. The rest is done by cups and hplip.
lsusb should list all devices that the kernel sees as USB. See if your printer is listed there. This will confirm that the USB port on your printer is functioning correctly.
And as nightflier mentions, there's a command like hp-makeuri that you'll need to run to give the correct info to cups. This is one area that we really need updated documentation on, I can't remember the specifics of what needs to be done here to get hplip and cups to run together. Maybe some generic hplip/cups documentation has the needed info?