Have had the 3110cn for quite awhile and am mostly pleased with it.  Several weeks ago, the main two people who use the printer somehow lost the ability to specify Duplex in Printing Preferences.  The Duplex option and the dropdown is just not there!!

BTW - Network connected printer

If I add this printer on a PC that has not used the printer before, same problem.  I have uninstalled driver on individual PCs, and even reinstalled on server to no avail.  My laptop has the Duplex option available (and always did) and it works just fine.

Any help would be appreciated.  The two without the option are the ones who most often use it!