There "was" a conflict with Firefox 3.5.5 in Windows XP which caused Firefox to crash if Virtualization was turned "On" in the Browser Security section of ZoneAlarm Extreme Security (version 9.1.008.000 and below) or in ZoneAlarm ForceField 1.3.153.000 (and below). ZoneAlarm updates have since been released to fix this problem.

ZONEALARM FORCEFIELD USERS:
Please ensure you are using the latest version of ZoneAlarm ForceField, which is available here:
http://www.zonealarm.com.au/main/updates.htm

ZONEALARM EXTREME SECURITY USERS:
Please ensure you are using ZoneAlarm Extreme Security 9.1.008.000 or above. If you are using an older version of ZoneAlarm (pre 9.1.008.000), download and install the latest version of ZoneAlarm Extreme Security, which is available here:
http://www.zonealarm.com.au/main/updates.htm

If you are already using version 9.1.008.000, please open ZoneAlarm Extreme Security by going to the Windows START menu, Program/All Programs, ZoneAlarm and click ZoneAlarm Security to open the main ZoneAlarm window. Click Overview on the left, Preferences below and then the "Check for Update" button on the right. Wait for the update process to complete, close the main ZoneAlarm window and restart the computer. Once you have restarted the computer, Firefox should now work well again with the Virtualization feature in ZoneAlarm Extreme Security.