I was reading a site on security today and others have expressed similar problems. Unless you have special configuration needs or want to configure programs in a certain manner (restricting certain apps to certain ports, for example) ZA free is just fine.
Although some people have no problems with 3.0 Pro, some do.
This is a bit late for you now I know, but anyone else thinking of upping their version may wish to hold off for a bit.
If you do decide to go back to the free version, I understand there is a bit of fiddling involved, but ZA should help if you get stuck.