I suspect that something, perhaps the SANE version, that changed from 13.10 to 14.04 is the actual problem.
You were right, the problem came from SANE. Looking through their documentation, I was able to find that the problem resided in /etc/sane.d/xerox_mfp.conf; the line for my printer was commented, and the printer was set in USB mode:
#Samsung SCX-3205W, usb mode
I uninstalled suld-driver-4.00.39 and installed 4.00.36, since, for some reason, 4.00.39 only lets me add the printer in DNS-SD mode (as opposed to tcp host address +port)
Rebooted, added the printer again via network address+port, then uncommented and edited the pertinent line in /etc/sane.d/xerox_mfp.conf so it looks like this:
#Samsung SCX-3205W, network mode
tcp host_address [port]
Problem solved. :)
Thanks for pointing me in the right direction! I hope this comes in handy - for future reference - for anyone else experiencing the same kind of problem.
Just for the record, for some reason, in Kubuntu 14.10 amd64, certain apps (e.g. Okular) are unable/unwilling to print when this printer is used in tcp address+port mode.
To get it to work, I had to add the printer again as an LPD network printer (DNS-SD) and make this printer default, while leaving the TCP-mode printer (how it was previously installed) untouched, so as to maintain scanner functionality.