I am having the same problem with Firefox 3.5.7 where I can't open a second window as long as the ZA tool bar is on.
My addons are:
AI Roboform Toolbar for Firefox 6.9.96
Google Toolbar for Firefox 6.1.20091119W
IE View 1.4.5
Yahoo! Toolbar 188.8.131.5290629
ZoneAlarm Toolbar 184.108.40.206
The IE works OK.
I am running ZoneAlarm Security Suite v: 9.1.008.000
Any idea how this problem can be fixed?