I am having similar issue, where my browser locks up. I have a netgear G modem.
I have:
-ZA security version:
-Dell xps m1530 laptop...2g ram
-Vista with SP2

After calling dell they told me to remove ZA completely because they have had similar problems with ZA. I removed ONLY the ZA tool bar from my browsers because when I upgraded to ZA 9.1, the toolbar was the newest addition on my laptop. So far I have no problems. (If the problem should come back then I will remove ZA altogether and see it that helps.) I have been purchasing ZA since 1999 and love the product, would hate to see it go.