Comment 6 for bug 278097

I have the same problem using xorg radeon driver (XT1600)

LANG=C apt-cache policy firefox
firefox:
  Installed: (none)
  Candidate: 3.0.3+build1+nobinonly-0ubuntu1
  Version table:
     3.0.3+build1+nobinonly-0ubuntu1 0
        500 http://gb.archive.ubuntu.com intrepid/main Packages

LANG=C apt-cache policy flashplugin-nonfree
flashplugin-nonfree:
  Installed: 10.0.1.218+10.0.0.525ubuntu1
  Candidate: 10.0.1.218+10.0.0.525ubuntu1
  Version table:
 *** 10.0.1.218+10.0.0.525ubuntu1 0
        500 http://gb.archive.ubuntu.com intrepid/multiverse Packages
        100 /var/lib/dpkg/status

dpkg -l | grep radeon
ii radeontool 1.5-5build1 utility to control ATI Radeon backlight func
ii xserver-xorg-video-radeon 1:6.9.0+git20081003.f9826a56-0ubuntu2 X.Org X server -- ATI Radeon display driver
ii xserver-xorg-video-radeonhd 1.2.1-2build2 X.Org X server -- AMD/ATI r5xx, r6xx display