Hi,
Sorry I should have mentioned all that information earlier. I run Arch Linux with KDEmod installed. Arch is a rolling distro so all my software is up to date with the lastest stable versions. KDEmod is KDE tweeked for Arch Linux. I use the KDEmod repositories namely the "core" and "extragear" ones.
When I run firefox there are no warnings. I also tried running firefox in safe-mode and that didn't make any difference. Thunderbird works fine. I also tried changing the firefox themes but that didn't really change anything.
Firefox is indeed the only application with this effect. Its really wierd. I stumped.
BFC