You'll not get many answers here as far as "best" av app. There just are not very many of us except those that just recently switched from Windows and a few that try to protect their windows using friends by not passing one along that use one. Consequently, there just aren't a lot of folks that have tried even one av app, much less several in order to suggest a "best".
There are as of yet, no virii in the wild that can affect OS X. It is possible the boss has a trojan if he's downloaded, installed and provided his master password to either pirated software or video codecs from porn sites. One of these would be re-directing his web browsing to pages he doesn't want to go to.
If that's not it, it'd be much easier telling what sort of issues there are and trying to find a fix for them. Could be a bad preference file, need a permissions repair or just a software glitch - they happen.