migration-assistant: imported firefox bookmarks not found on installed system

Precise Desktop 20120419

Test Setup:
2 existing OS before installation of Precise:
* sda5:
  - lucid i386 french
  - 1 user named 'lucid'
  - 2 bookmarks added to firefox
* sda6: oneiric i386 french
  - 1 user named 'oneiric'
  - 2 bookmarks added to firefox different from lucid
* sda7: free space for new installation

TEST CASE:
1. Install Ubuntu Precise Desktop French on sda7
2. In m-a, select all the available items in the list.
  During this test, migration assistant recognized both installations and asked to import firefox bookmarks for both (Only FF bookmarks was listed)
3. Proceed with the installation
4. Reboot to 12.04LTS and login
5. Launch Firefox and check that bookmarks were imported

ACTUAL RESULT
After installation and reboot to newly installed 12.04 LTS imported bookmarks are not found in Firefox.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 3.2.0-23.36-generic-pae 3.2.14
Uname: Linux 3.2.0-23-generic-pae i686
ApportVersion: 2.0.1-0ubuntu5
Architecture: i386
Date: Fri Apr 20 14:27:04 2012
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta i386 (20120419.1)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)