I've had PortableApps.com's version of Firefox running on my thumb drive for quite a long time and have never experienced this issue before. Upon installing the latest version of Firefox (3.5), I noticed that Firefox automatically closes when I try to view a page that contains graphs requiring Adobe SVG Viewer under IE. The interesting thing is that the full version of Firefox 3.5 (non-portableapps) does not have the same problem.
Can someone help me resolve this issue? More details are available upon request.