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 220.127.116.1190629
ZoneAlarm Toolbar 18.104.22.168
The IE works OK.
I am running ZoneAlarm Security Suite v: 9.1.008.000
Any idea how this problem can be fixed?