sorry, been out.
ah, so it's definetly the java upgrade (out of interest any windows update files get done also? just in case although prob java)
you have rebooted haven't you ? firefox needs a restart after java upgrade, but full reboot always advised.
I assume you are running microshaft xp or veesta ?
add remove programs, uninstall java, reeboot, then either get the older version that worked & reinstall or go for the new one again but after reboot obviously.
let me know if you want to troubleshoot it.....