Troubleshooting Xerox printers

Over the last few days, we've received a trio of reports about Xerox printers:

Al Spiegleman writes: "Xerox Phaser 840: sometimes background on items that should be white (clear) print out with pale yellow. Xerox sent me new firmware for the printer and it fixed this."

Lon Nesseler adds: "According to Xerox, the reason the Print dialog for my Phaser 860DP doesn't include the ability to set the print quality is that some HP laser printer drivers (in my case, a 4050N) install a .PDE file that interferes with the options of other PostScript printers."

Jeff Flamm found: "With my Xerox Phaser 790 color printer, since switching to OS X 10.1.x (including 10.1.2), I have been unable to address the optional features of printer such as duplex printing, selecting alternate paper trays, transparencies etc."