About Virus Barrier please go to Apple Store and take a look at users comments.
To be perfectly blunt, the people posting the poor reviews of VirusBarrier Express on the App Store know less than crap about it. They're so uninformed it's actually comical. Keep in mind that I have a substantial collection of Mac malware and have tested most Mac anti-virus apps, so I have factual data to back up which ones perform and which ones don't:
http://www.thesafemac.com/mac-anti-virus-testing-01-2013/
Let's consider some examples of those reviews. One guy says that it's "scant on virus definitions," and that iAntivirus is the best. That's just positively libelous when you look at my test results. Especially the part about iAntivirus, which is really not good.
How about the guy who says it doesn't find "trojan viruses" and that McAfee does better? Once again, see my testing... McAfee's worse than iAntivirus. Plus, anyone who gives advice on this topic while using the term "trojan viruses" should immediately be discounted, since there's no such thing. That's like telling people visiting India to beware of mosquito cobras... sticking two words together doesn't mean the combination makes sense.
How about the guy saying updating of malware signatures is inconsistent... because there hadn't been any updates for 13 days, between May 17 and May 30 of 2012. Sure, that's bad in the Windows world... in the Mac world, new malware doesn't occur very often. There probably wasn't any need to update the signatures during that time! There was a bunch of new malware that appeared during Feb - April of 2012, but none in May. (Assuming, of course, that he actually knew how to update the signatures and didn't have some other software blocking the connection, which could also be contributing factors for all we know.)
Similarly, the guy who says the definitions can't be updated clearly had something wrong, probably something like Little Snitch blocking the connection attempt, because the definitions update extremely quickly and easily.
Regarding some of the crash reports... well, software can always crash. I can't say that's impossible, though I haven't ever had VBE crash on me. I do have to say it seems unlikely that an App Store app - any App Store app - could cause a "black screen of death." Most likely there were some other factors at play there.
In other words... please don't post advice about this sort of stuff if you really don't have the facts.