i dont know if its releated but you can try upgrading to the latest fiirmware version : 061.090.221.04800 , you can obtain this by calling xerox support...
i see in the release notes that it fixes jams scanning a specific format
We have a Workcentre 7765 which, more often than not, gets paper jams (typically) after the first page scans. With my past experience with scanning based machines it usually has something to do with the sensor. However, it seems like the sensor on this machine is an optical sensor within the automatic feed tray. I messed around with this by putting my finger over it, then off, then on to see how it responds (and because I didn't know what else to do with the thing).
I was then able to scan 4 or 5 pages with no problem. I did this a couple of times and all seemed to work just fine, until the next day (today). Twice a user tried scanning a couple of pages and each time it jammed. When I came by to check, it scanned fine the first time. After that it would jam, one time with the first page and another on the fourth page, but mostly after the first page scanned. I tried playing wtih the sensor, but that didn't work.
We've had this machine (as well as 3 other multifunction machines) for about 4 months, so it's not old. Any ideas, suggestions, answers are greatly appreciated.