Is this a recent version of Firefox? Are you using the embedded dev tools, or are you trying to use Firebug? Chances are your issue comes from a buggy plugin.

Is this a recent version of Firefox? Are you using the embedded dev tools, or are you trying to use Firebug? Chances are your issue comes from a buggy plugin. I've filled my share of Firefox bug reports, but lately most problems I run into are due to buggy plugins.