Reinstall the driver, and not an MS class driver, get it from Xerox.com. Because whatever you have done to the one you have, you are sending Booklets that can't be done, and since you state you can't print test pages, that means you have really broken the one you have.
Printer
Status Indicator RAP
016-738 Invalid paper size for PS booklet print.
Procedure
Perform the steps that follow:
1. Advise the customer to specify the the correct settings that allow booklet printing.
It's hooked up via USB. This is on an x86 Windows 7 computer.
Pages it could print before were giving the above error. Now it's giving the error even with test pages. Have tried a bunch of different things from drivers to changing virtual memory size. Anyone have any advice on what to do/try?