You are using an out-dated version of Firefox (Mozilla Foxfire 3.0.1.1). The current version is 3.5. I suggest you first update to the latest version. If that doesn't solve the browser crashes, I suggest that you run Firefox in
Safe Mode, disabling all add-ons. You will have to enable the add-ons one-by-one to find the culprit.
Otherwise, it is possible there is a conflict between your firewall and another software on your computer -- although I don't know which or if that is actually the case. What you could try is disconnecting from the internet, disable your current firewall and activate the Windows Firewall. If that solves the problem of crashes, then I suggest you switch to a different firewall.