I've installed a number of MF634Cdw for my clients. Almost all have been trouble-free.
In one case, though, this small office has trouble from all the (Win7) workstations. The printer is on the network. Drivers are installed per-computer with default settings, not shared from the domain server. Print jobs simply stick in the queue. Restarting the job in the queue only fixes the problem now and then. I've tried tweaking the usual spooling options as well as disabling the Printer / Properties / Device Settings spooling and nothing makes a difference. I've updated the firmware on the printer. It's not just the print jobs from one app, it happens from several.
Any ideas?