I have a Versalink C405 (which I think is a brand new model) with duplex printer on my network. Currently on all the computers I have installed the printer (running a variety of Windows versions) the option for 2-sided printing is greyed out. I have tried re-installing the drivers multiple times, using the automatic online tool, but same problem always arises.
On one of the computers I somehow managed to get 2-sided working, but had lots of problems communicating with it. It would just tell me the printer was offline most of the time. I decided to re-install the drivers recently to solve that problem, which worked, but again 2-sided printing was subsequently greyed out.