i had true vector errors with xp home and a really old version of zonealarm about 2 years ago but none since.
if you are using the latest version im not sure. what operating system are you using? if its xp check 'control panel/administrative tools/event viewer' and click on the 'system' and 'application' tabs and look for errors listed here, what do they say?
is windows itself all up to date? if not click here
also try the ZA forums click here and you will see a lot of truevector error postings like click here
some more info may help a bit sorry.