Apple keeps changing the rules for SMB/AFP, then Xerox needs to change their firmware to match the new settings, which leads to the user needing to call up for Spar Firmware every time scan breaks.
The new Xerox firmware is here for your 7835, install it only if your current firmware starts with 072, if it starts with 071 call Xerox and have a tech upgrade it via the "Altboot no data backup, no clone" method, but beware, this will wipe every setting off the machine and make it like it was brand new right out of the box, everything you ever did will be erased. Which is another reason to just stick to FTP when using Macs, and remember, even if you fix it now, 10.11 is set to go out as a preview in June 2015 (one month) and the full release should be this fall, which will likely change things for scan again. And going by previous updates 10.6.8/10.8/10.9 and 10.10, will also bring with it some print problems as well.