Many thanks to tom, rockdalinux and monk for your helpful replies.Unfortunately, none of the ideas worked (I have the equivalent of the Debian cupsys-bsd, lpc is correctly installed, and cups is running).

However, by playing around I found that I could print if I installed the Sun j2sdk 1.4.2 in place of the more recent jdk 1.5.0. Checking bug reports on the Sun website showed that this problem has been described before and supposedly fixed (see http://bugs.sun.com/bugdatabase/index.jsp) (bug ID 5109523 is particularly relevant). Proposed workarounds included:
1. disabling authentification in CUPS, or
2. using Jipsi to allow specifying a username/password to select an IPP print service.

Neither of these seems valid, particularly since Jipsi is no longer required by CUPS for discovering the print services. So I was left with the choice of using the old j2sdk 1.4.2 and being deprived of recent improvements (but being able to print) or forgetting about printing and using a recent Sun Java VM.

By chance I found that IBM release a Java VM: I installed their latest version (IBM j2se 5.0) and it works just fine! The print services are discovered, the printers are listed, no problem printing, and I have the feeling that the apps themselves run faster.

I will stick with IBM java VM,, but to satisfy my curiosity in this matter could you tell me which java versions you are/were using for successful printing?

Thanks again, look forward to your replies,
Mike