I'm on the PS driver instead of the raster driver and have gotten that message since upgrading to 10.5 quite some time ago. It has never actually been more than annoying message for me, however. I always assumed that it was just a quirk of the Postscript driver. I look at it as my printer swearing at me. I suspect you have a networking issue, and would check your settings, since you probably had to reset many things with the upgrade. The message may be a symptom of another issue, but I would not take it alone as a fatal flaw, as it has never caused me more than a little consternation. Are you setting your printer up to connect via HP JetDirect, USB, or another method?