Debian :: Scanner No Longer Recognized After Update

I am running Wheezy 7.9 32 bit, with the kernel Linux 3.2.0-4-686-pae, and Gnome 3.4.2 on an Intel Pentium CPU G3420 @ 3.2 GHz. I installed a new printer in August, an HP Officejet 7612 all-in-one printer/scanner/copier, and it worked perfectly as both a printer and a scanner first time, despite not being listed on the supported list in SANE. Two weeks ago, I got a general software update notification, and did the update. Now the scanner is not recognised. The printer still works fine as a printer, but when using Simple-scan, I get the error message "No scanners detected. Please check your scanner is connected and powered on". I have had a look round on Google, and all the suggestions made do not work.

I tried the suggestion to add myself to the scanner users list on my PC which made no difference (even though the scanner previously worked without my being added to the scanner users list).

I have deleted the printer and re-installed it using CUPS, but that still has no effect. I tried re-installing HPLIP also to no avail, and I have now lost the toolbox on the drop down menu under <Applications> <Accessories> <HP Toolbox>, as when I click on it, nothing happens.

It would seem that something in the update has messed up Simple-scan. Looking at the dpkg log (is this the right thing to look at?) for the date of the update, I cannot find anything which directly involved SANE, so I think that it might be something else which has affected SANE. How I can find out which update did the damage? I don't normally do anything except accept recommended updates, so I am a bit lost as to what to do.