Communication error on mutlipage adf hp 2840

[Schmirrwurst]

Using lastest version of hplip : 2.12.6 on ubuntu 12.10 with hp color laserjet 2840

When trying to scan multiple pages through the automatic document feeder, the following appends :

- the first page scan properly, on the middle of the page, the process ist stopped on the application side (the rest of the page is not displayed), and a warning to check the scanner availability is appearing on simplescan.
On the printer, the display is still displaying "reservered for scanning by pc"
here the logs
Jul 27 12:39:30 araora simple-scan: io/hpmud/dot4.c 121: unexpected DOT4CreditRequest: cmd=4, hid=1, pid=1, maxcredit=8
Jul 27 12:40:50 simple-scan: last message repeated 4 times
Jul 27 12:43:19 araora kernel: [ 9971.024058] usb 2-2: reset full-speed USB device number 3 using ohci_hcd
Jul 27 12:43:20 araora kernel: [ 9971.236544] usblp0: USB Bidirectional printer dev 3 if 0 alt 1 proto 2 vid 0x03F0 pid 0x2817
Jul 27 12:43:20 araora kernel: [ 9971.239981] usb 2-2: usbfs: process 3584 (simple-scan) did not claim interface 0 before use
Jul 27 12:43:20 araora simple-scan: io/hpmud/dot4.c 688: unable to write Dot4Credit: Succès
Jul 27 12:43:20 araora simple-scan: invalid read: exp=1268 act=796 ReadMfpdtfBlock scan/sane/mfpdtf.c 527
Jul 27 12:43:20 araora simple-scan: io/hpmud/dot4.c 436: unable to write Dot4ForwardData header: Succès
Jul 27 12:43:20 araora simple-scan: io/hpmud/pml.c 375: SetPml channel_write failed ret=12
Jul 27 12:43:20 araora simple-scan: io/hpmud/dot4.c 649: unable to write Dot4CloseChannel: Succès
Jul 27 12:43:20 araora simple-scan: io/hpmud/dot4.c 649: unable to write Dot4CloseChannel: Succès
Jul 27 12:43:20 araora simple-scan: io/hpmud/dot4.c 358: unable to write DOT4Exit: Succès
Jul 27 12:43:20 araora kernel: [ 9971.242034] usb 2-2: usbfs: process 3586 (simple-scan) did not claim interface 0 before use
Jul 27 12:43:20 araora kernel: [ 9971.242429] usb 2-2: usbfs: process 3587 (simple-scan) did not claim interface 0 before use
Jul 27 12:43:20 araora kernel: [ 9971.242678] usb 2-2: usbfs: process 3588 (simple-scan) did not claim interface 0 before use
Jul 27 12:43:20 araora kernel: [ 9971.242907] usb 2-2: usbfs: process 3589 (simple-scan) did not claim interface 0 before use
Jul 27 12:43:20 araora udev-configure-printer: add /devices/pci0000:00/0000:00:0b.0/usb2/2-2/2-2:1.0/usb/lp0
Jul 27 12:43:20 araora udev-configure-printer: device devpath is /devices/pci0000:00/0000:00:0b.0/usb2/2-2
Jul 27 12:43:20 araora udev-configure-printer: Device already handled

- with gscan2pdf, the feeder seems to process every pages, but thy don't appear on the app, the log file show the following :
Jul 27 12:35:22 araora perl: io/hpmud/dot4.c 121: unexpected DOT4CreditRequest: cmd=4, hid=1, pid=1, maxcredit=8
Jul 27 12:36:50 perl: last message repeated 4 times