Observation, installed ZAISS 9.1.507.000 this morning. The ZoneAlarm Toolbar 220.127.116.11 was added to my FireFox 3.6.3. Thereafter I had problems with FireFox in that only one instance of FireFox could be running at one time. I had to disable the ZoneAlarm Toolbar before I could run multiple instances of FireFox.
Just reporting what I saw. After disabling the ZoneAlarm Toolbar, all works as expected again.