I have the same issue, and with me, it is not a keychains issue.
In the past, my Brother HL-2030 laser printer was connected to my DSL modem (a Telekom Austria Pirelli PRGAV4202N). After entering its IPP URL, that worked perfectly.
With Lion, this has stopped working, showing exactly the symptoms you described (printer goes to pause immediately).
Today, I have moved the printer from the Pirelli modem to my Iomega StorCenter ix2-200 NAS which supports USB printing, too.
With the NAS, printing does not work, either, but the symptoms slightly vary. In the beginning, there is a slight improvement: When I click the "+" icon for adding a printer, the printer shows up in the list! (This is new - with the Pirelli modem, I had to manually enter the IPP URL.)
But as soon as I try printing, the printer queue dialog (German MacOS) shows "Drucker suchen" ("searching for a printer") for a few seconds, and then the printer dialog shows the printer as paused ("Angehalten.") with the additional information "Drucker ist nicht angeschlossen" ("printer is not connected").
When selecting the blue "i" (print job info), the information "Auftragsnachricht: Der Drucker-URI ist falsch oder existiert nicht mehr." (literally: "print job message: The printer URI is wrong or does not exist any longer".)
This is really annoying, and I am desparately looking for a solution, too.