I've experienced the problem described in this URL and the code fix given corrected it. I tried sending the print from linux (RH5.2) and HP-UX 10.20. I'm using lpr-0.35-1, with the HP LaserJet 4/5/6 series smart filter on a Pentium based system. http://www.us.berlin-consortium.org/Bugs/db/36/36794.html RH 5.2 does not appear to have this problem.
Try the latest lpr from Raw Hide - this should fix your problem (please re-open if it doesn't.)