I have been through all the suggestions from Firefox Forum and Zone alarm suggestions on this thread.
Firefox / IExplorer/Google Chrome have all been freezing for the last few weeks on my Laptop running Vista Premium.
I have now uninstalled the Free Zonealarm and running Windows firewall.
I have not had a freeze since, even leaving the laptop in hibernation mode with Chrome open as started up without a fault.
My conclusion must be that Free Zone Alarm is the problem.
It is a pity because I have always used Zone Alarm from the start.