Arch Linux

Due to a lot of updates (and also due to mixing some packages from testing and stable repository) I came into a situation where pacman cannot evaluate the packages that have been already updated.
pacman -Syu gives the following messages:
[root@teo ~]# pacman -Syu
error: /var/lib/pacman/local/-/desc: No such file or directory
:: Synchronizing package databases...
:: current is up to date
:: extra is up to date
:: Replace raidtools with mdadm from "current"? [Y/n] Y
error: /var/lib/pacman/local/-/desc: No such file or directory
error: /var/lib/pacman/local/-/desc: No such file or directory
error: /var/lib/pacman/local/-/desc: No such file or directory
[ ... and so on ...]
error: /var/lib/pacman/local/-/desc: No such file or directory
error: /var/lib/pacman/local/-/desc: No such file or directory

Remove: raidtools

Targets: kernel-headers-2.6.18.1-1 glibc-2.4-4 mdadm-2.5.5-2 coreutils-6.4-2 findutils-4.2.28-1 gettext-0.15-1 man-pages-2.41-1 pciutils-2.2.4-1 curl-7.15.5-1 libxml2-2.6.26-1
libgpg-error-1.4-1 libgcrypt-1.2.3-1 libxslt-1.1.17-1 freetype2-2.2.1-3 libjpeg-6b-4 libpng-1.2.12-1 php-5.1.6-4 udev-103-1

Total Package Size: 30.1 MB

Proceed with upgrade? [Y/n] n

The same packages are shown as "old" even if I had already done more updates. Pacman skips the download phase but trying to install the packages it says that file exists. So , the only way I can update a package is using "pacman -Sf the-package" and it installs a lot of other related packages that are (I am sure) already downloaded and updated.

Is there an option to pacman that rebuilds the local packages version database?

Thanks in advance,
Teo