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 126.96.36.19990629
ZoneAlarm Toolbar 188.8.131.52
The IE works OK.
I am running ZoneAlarm Security Suite v: 9.1.008.000
Any idea how this problem can be fixed?