I performed the following steps and it corrected the preview problem in Firefox: On my CentOS Server: $ yum install zlib-devel libjpeg-devel giflib-devel freetype-devel gcc gcc-c++ $ wget http://www.swftools.org/swftools-0.9.2.tar.gz $ tar xzf swftools-0.9.2.tar.gz $ cd swftools-0.9.2 $ ./configure ...