I just installed ZoneAlarm Extreme Security. I updated Forcefield to the most recent version available for Firefox. Firefox version 5.5.
I am running the most recent Firefox 3.6. This may explain the following error message I receive when trying to enable the ForceField toolbar:
unload: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIObserverService.removeObserver]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: chrome://trustchecker/content/trustchecker.js :: anonymous :: line 949" data: no]
After seeing this message, I cannot see the ForceField toolbar but there is a checkmark in the context menu by the ForceField name. This checkmark is to indicate that the FF toolbar is enabled but I cannot see it.
Later, I turned off the toolbar (and the checkmark is gone). By turning the toolbar off, I am presented with the same error message shown above.
Let me know if you need anymore information. I hope this helps