classes with different printers

[lijews]

Hi,

I'm trying to set up two network printers: HP and Dell to work with HP as primary printer and Dell as a secondary. I'm mean, users generaly should print their documents on the HP, and Dell should be used only when HP is busy.
I tried to organize both of the printers into class, but I observe strange behaviour: the first job is send to HP, and the next to Dell, then next to HP, and next to Dell, and so on, even when then on the HP is finished. I can even wait whole day, restart cups, and  the next job is still send to another printer, than the previous job.
Even worse: I can switch off the HP (or Dell), so in cups it get status: not connected, and the job is send to this printer.
I've tested it on cups 1.1 (suse10 SP2), cups 1.3 (sled 11) and cups 1.3 (gentoo).
What can be wrong? I'm using AppSocket as a device uri.