suse 10.2, CUPS 1.2.7: cupsdAuthorize: Local authentication certificate not found!

[ekkard gerlach]

Hi,
using Suse 10.2, I can't print to /dev/usb/lp0. Printing to DeviceURI 
usb://HP/LaserJet%201022  works fine. I need to print to /dev/usb/lp0 
because I need to install serveral identical (!) printers to a PC. Then 
I configure one printer to /dev/ubs/lp0 the second to /dev/ubs/lp1, and 
so on.  Suse 9.2 with an older CUPS works fine using /dev/usb/lpX 
directly. Why does CUPS 1.2.7. not allow printing to /dev/usb/lpX?

BTW: echo xxxxx > /dev/usb/lp0 works, the printer starts and tries 
printing.

/var/log/cups/err_log:
[...]
D [05/Aug/2009:22:51:08 +0200] cupsdProcessIPPRequest: 7 status_code=0 
(successful-ok)
D [05/Aug/2009:22:51:11 +0200] cupsdReadClient: 7 POST / HTTP/1.1
E [05/Aug/2009:22:51:11 +0200] cupsdAuthorize: Local authentication 
certificate not found!
D [05/Aug/2009:22:51:11 +0200] Get-Printer-Attributes 
ipp://localhost/printers/R220_usblp0
D [05/Aug/2009:22:51:11 +0200] cupsdProcessIPPRequest: 7 status_code=0 
(successful-ok)
D [05/Aug/2009:22:51:11 +0200] cupsdReadClient: 7 POST / HTTP/1.1
E [05/Aug/2009:22:51:11 +0200] cupsdAuthorize: Local authentication 
certificate not found!
D [05/Aug/2009:22:51:11 +0200] Get-Jobs ipp://localhost/printers/R220_usblp0
D [05/Aug/2009:22:51:11 +0200] cupsdProcessIPPRequest: 7 status_code=0 
(successful-ok)
D [05/Aug/2009:22:51:11 +0200] cupsdReadClient: 7 POST / HTTP/1.1
E [05/Aug/2009:22:51:11 +0200] cupsdAuthorize: Local authentication 
certificate not found!
D [05/Aug/2009:22:51:11 +0200] Get-Printer-Attributes 
ipp://localhost/printers/R220_normal
D [05/Aug/2009:22:51:11 +0200] cupsdProcessIPPRequest: 7 status_code=0 
(successful-ok)
D [05/Aug/2009:22:51:11 +0200] cupsdReadClient: 7 POST / HTTP/1.1
E [05/Aug/2009:22:51:11 +0200] cupsdAuthorize: Local authentication 
certificate not found!
D [05/Aug/2009:22:51:11 +0200] Get-Jobs ipp://localhost/printers/R220_normal
D [05/Aug/2009:22:51:11 +0200] cupsdProcessIPPRequest: 7 status_code=0 
(successful-ok)

thx
Ekkard