MPF Tray Issues - 5100cn

I have also had a similar problem. When I try to print irregularly-sized paper in the MPF tray, I get a "Load Paper" error. I have created a custom paper size in Word and changed all the options I could in the printer properties, but I still get the same error. Cancelling and restarting the print job sometimes allows me to print one or two copies, but that's it! The copies that it does print are dead-on, positioned correctly. However, I don't want to stand here and print one or two at a time, when I am trying to print a couple thousand copies! My Dell support rep had no suggestions for me, and I hoped to get the board's response on this issue. (BTW, almost every other printer in our office is an HP, and this is our first foray into Dell's printers. I hope this is not indicative of their capabilities.)