system incredibly slow

[Luca Ferrari]

Today my system, based on 12.10, started to be unresponsive. First of
all, yesterday it worked as a charm and I did not any update/upgrade.
Today the system, after the login, started to bee very slow and opened
the dolphin on my home folder (I have setup to start with a clear
session, so this is quite strange). Any kde based application is
unresponsive, while non-kde or non-qt applications (like firefox) work
fine. In order to understand just to open dolphin it takes up to 1
minute!

My kernel is 3.2.0_52 on x64, I've 4 gigabyte sof ram, sata hdd, kde
is now at 4.11.2.
Since this strange behavior, I did an apt-get upgrade today but nothing changed.
I've nepomuk disabled, but I see a lot of cpu is consumed by
plasma-desktop and akonadi notifications. I've tried to kill all
akonadi processes, as well as zeitgeist based ones, but nothing
changed.

Any suggestion about how to get usable my machine again?

Thanks,
Luca