I recently upgraded to ZA Extreme Security v9.1.507.000, Everything went well and there were no major upgrade problems. However, I noticed with this version that when ZA does its automatic signature upgrades my computer grinds to a halt (e.g, keyboard doesn't accept input, browser freezes in mid-tranmission, etc...) and everything kicks in again once the signature update is completed.
This didn't happen with previous versions.
Windows XP SP3 (all patches/updates applied)
ZoneAlarm Extreme Security 9.1.507.000