Dear Maintainer,
After upgrading plasma4 to plasma5 (including package kwalletmanager) and reboot multiple times, I got a warning telling me that my hard drive was full.
After investigation, files /var/log/message /var/log/syslog and others were a size greater than 1Go, which contains lines like
KConfigIni: In file /boot/vmlinuz-4.0.0-1-686-pae, line 12124: " Invalid entry (missing '=')
for all files in /boot/.
If I believe this ticket (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=747665), it's a problem in localepurge that impact KDE.
I solved my problem by also applying the commands of the same ticket (in summary, required to reconfigure localepurge without option --path-exclude and reinstall kde/kwalletmanager).
Thanks and good luck.