As mentioned above... Spent some time in Mizoilla's Firefox Support forum. It seems to only be a problem with Norton Internet Security (NIS), which came with this box (and which I'll replace with ZoneAlarm when the subsription runs out).

The workaround (for WinXP):

-- Close all instances of Firefox

-- Open NIS, highlight "Personal Firewall", click the "Congfiure" button which appears in the lower right corner.

-- When the Configure window opens, go to the "Programs" tab. Uncheck the "Automatic Program Control" box. Then scroll down the Manual Program Control list to "Firefox". Highlight it, and click the "Remove" button. NIS will tell you that it will ask permission next time you open Firefox; click "OK".

-- Leaving NIS open to the Config window, now start Firefox, and note that NIS may ask you about permission, but will not actually update the config list.

-- Close FF again, then click the "Add" button on the NIS Config window. It'll take you to the Program Items folder. Find and highlight firefox.exe, then click Open (or double-click).

The results should be: [1] Firefox is added to the Manual Program Control List; [2] It should connect to the Net the next time you start it.