~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04 LTS"

~$ uname -a
Linux dark 3.2.0-26-generic #41-Ubuntu SMP Thu Jun 14 17:49:24 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

~$ dpkg -s firefox
Package: firefox
Status: install ok installed
Priority: optional
Section: web
Installed-Size: 41918
Maintainer: Ubuntu Mozilla Team <ubuntu-mozillateam@lists.ubuntu.com>
Architecture: amd64
Version: 14.0.1+build1-0ubuntu0.12.04.1
Replaces: abrowser, abrowser-branding, firefox-branding, kubuntu-firefox-installer
Provides: gnome-www-browser, iceweasel, www-browser
Depends: lsb-release, libasound2 (>= 1.0.23), libatk1.0-0 (>= 1.12.4), libc6 (>= 2.15), libcairo2 (>= 1.2.4), libdbus-1-3 (>= 1.0.2), libdbus-glib-1-2 (>= 0.78), libfontconfig1 (>= 2.8.0), libfreetype6 (>= 2.3.9), libgcc1 (>= 1:4.1.1), libgdk-pixbuf2.0-0 (>= 2.22.0), libglib2.0-0 (>= 2.31.8), libgtk2.0-0 (>= 2.24.0), libpango1.0-0 (>= 1.14.0), libstartup-notification0 (>= 0.8), libstdc++6 (>= 4.6), libx11-6, libxext6, libxrender1, libxt6
Recommends: xul-ext-ubufox, firefox-globalmenu, libcanberra0
Suggests: latex-xft-fonts, libthai0, firefox-gnome-support | firefox-kde-support
Breaks: abrowser (<= 4.0~b11+build3+nobinonly-0ubuntu1), abrowser-branding (<= 4.0~b11+build3+nobinonly-0ubuntu1), adobe-flashplugin (<= 11.1.102.63-0precise1), firefox-branding (<= 4.0~b11+build3+nobinonly-0ubuntu1), flashplugin-installer (<= 11.1.102.63ubuntu1)
Conflicts: gcu-plugin (<= 0.12.10-1ubuntu1)
Conffiles:
 /etc/apparmor.d/usr.bin.firefox 1e9622ff54b66ff14df4cbd6987599d9
 /etc/apport/blacklist.d/firefox ee63264f847e671832d42255912ce144
 /etc/apport/native-origins.d/firefox 7c26b75c7c2b715c89cc6d85338252a4
 /etc/firefox/syspref.js 09e457e65435a1a043521f2bd19cd2a1
Description: Safe and easy web browser from Mozilla
 Firefox delivers safe, easy web browsing. A familiar user interface,
 enhanced security features including protection from online identity theft,
 and integrated search let you get the most out of the web.
Xul-Appid: {ec8030f7-c20a-464f-9b0e-13a3a9e97384}

Error Console log right after startup (nothing suspicious from my point of view):
Could not read chrome manifest 'jar:file:///usr/lib/firefox/extensions/langpack-en-GB@firefox.mozilla.org.xpi!/chrome/en-GB.manifest'.
Could not read chrome manifest 'jar:file:///usr/lib/firefox/extensions/langpack-ja@firefox.mozilla.org.xpi!/chrome/ja.manifest'.
Could not read chrome manifest 'jar:file:///usr/lib/firefox/extensions/langpack-en-ZA@firefox.mozilla.org.xpi!/chrome/en-ZA.manifest'.
Could not read chrome manifest 'file:///usr/lib/firefox/extensions/%7B972ce4c6-7e08-4474-a285-3208198ce6fd%7D/chrome.manifest'.
While creating services from category 'profile-after-change', service for entry 'updateRestartNotifier', contract ID '@ubuntu.com/update-restart-notifier;1' does not implement nsIObserver.
No chrome package registered for chrome://ubufox/skin/overlay.css
Timestamp: 07/21/2012 12:44:56 AM
Warning: Unknown property '-moz-border-radius'.  Declaration dropped.
Source File: about:startpage
Line: 56

about:support page from clean profile with reproduced bug:

  Application Basics

        Name
        Firefox

        Version
        14.0.1

        User Agent
        Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:14.0) Gecko/20100101 Firefox/14.0.1

        Profile Directory

          Open Directory

        Enabled Plugins

          about:plugins

        Build Configuration

          about:buildconfig

        Crash Reports

          about:crashes

        Memory Use

          about:memory

  Extensions

        Name

        Version

        Enabled

        ID

        Global Menu Bar integration
        3.2.5
        true
        globalmenu@ubuntu.com

        Ubuntu Firefox Modifications
        2.1.1
        true
        ubufox@ubuntu.com

        url-addon-bar
        0.1.4
        true
        urlAddonBar@zbinlin

  Important Modified Preferences

      Name

      Value

        browser.cache.disk.capacity
        1048576

        browser.cache.disk.smart_size.first_run
        false

        browser.places.smartBookmarksVersion
        4

        browser.startup.homepage_override.buildID
        20120713224749

        browser.startup.homepage_override.mstone
        14.0.1

        extensions.lastAppVersion
        14.0.1

        network.cookie.prefsMigrated
        true

        places.history.expiration.transient_current_max_pages
        97022

        privacy.sanitize.migrateFx3Prefs
        true

  Graphics

        Adapter Description
        ATI Technologies Inc. -- ATI Radeon HD 3200 Graphics

        Vendor ID
        ATI Technologies Inc.

        Device ID
        ATI Radeon HD 3200 Graphics

        Driver Version
        3.3.11627 Compatibility Profile Context

        WebGL Renderer
        ATI Technologies Inc. -- ATI Radeon HD 3200 Graphics -- 3.3.11627 Compatibility Profile Context

        GPU Accelerated Windows
        0

        AzureBackend
        skia

  JavaScript

        Incremental GC
        1

  Library Versions

        Expected minimum version

        Version in use

        NSPR
        4.9
        4.9

        NSS
        3.13.5.0 Basic ECC
        3.13.5.0 Basic ECC

        NSS Util
        3.13.5.0
        3.13.5.0

        NSS SSL
        3.13.5.0 Basic ECC
        3.13.5.0 Basic ECC

        NSS S/MIME
        3.13.5.0 Basic ECC
        3.13.5.0 Basic ECC