Problem solved: I found out that I could upgrade kdeprint to the debugging version without having to upgrade all the KDE packages, so I reran valgrind in verbose mode and noticed that kprinter died just after trying to access /usr/lib/libcups.so.2. I upgraded cupsys, libcupsys2, and libcupsys2-dev from 1.1.19final-1.4 to 1.1.20final-16, and everything now works fine.