Hi Bonnie, and thanks for your question....of course you have a very high end printer, but laser printers have one major drawback...The paper runs through the fuser after it prints one side to "burn" the toner (which is mostly plastic and iron shavings) onto the paper. The fuser is around 300-350 degrees. Well, since you are manually duplexing, the paper is running through the fuser twice. i believe this may be burning the glossy coating on the paper.
Have you tried it with matte paper to see if you get the same results?? I dont think this is a problem with the printer, but more of an issue with the paper type...
Information Systems Manager
MCTS (Microsoft Certified Technical Specialist), A+, Network+, Security+