HPLIP: I/O Error after scanning a few pages

[Schmolch]

im using HPLIP since a while and before that i used HPOJ for many years.
Now and then things break and i guess it was about time for another incident.

My Printer is a HP LJ 1220 (Laserjet with Scanner-Attachment) and i
already scanned many books with it.

This is the error in /var/log/messages which i get after scanning a
couple of pages in batch-mode (ADF):

Aug 20 23:15:01 lap hpiod: invalid MlcReverseData state: unexpected
packet hsid=4, psid=4, cmd=2
Aug 20 23:15:01 lap hpiod: trying MlcReverseReply firmware hack:
io/hpiod/mlc.cpp 250
Aug 20 23:15:01 lap hpiod: [0000] 10 00 00 08 00 02 ......
Aug 20 23:15:01 lap hpiod: unsolicited data packet: hsid=10, psid=0,
length=8, credit=0, status=2: io/hpiod/mlc.cpp 102
Aug 20 23:15:01 lap hpiod: [0000] 10 00 00 08 00 02 00 01 ........

At this point the scanning stops and the printer's LEDs go nuts (i
think they blink in the same pattern like they do on startup).
Now, i have 2 Laptops, both running Gentoo Linux (unstable), both have
the same issue.
Laptop 1 though has not been updated since a while, but i cannot tell
for sure that since the last successfull scans, which must have been
about 4-6 weeks ago, nothing was updated.
Laptop 2 is updated quite often and i just updated HPLIP to 1.6.7 on it.

I would be very grateful for any advice.