language pack upgrade broke firefox search language

After upgrading to the latest italian language pack the firefox search doesn't work anymore as expected: every search from the address bar is performed using the english version of google, every google product (accessed from the dark grey toolbar) is started in the english version. E.g. Google maps starts with the view centered on USA.

My google settings are correct, my firefox home page and my sistem language settings, too.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: language-pack-it 1:12.04+20120508
ProcVersionSignature: Ubuntu 3.2.0-24.38-generic 3.2.16
Uname: Linux 3.2.0-24-generic x86_64
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
Date: Sat May 12 13:43:20 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120328)
PackageArchitecture: all
SourcePackage: language-pack-it
UpgradeStatus: No upgrade log present (probably fresh install)