I've found that after  the trial period using Comodo Anti-virus, and I didn't purchase it, they infected my computer.
So much for trust.  Even  so, I  still like Comodo, the way it's set up, and am considering purchasing it. Now I'm running AVG on trial, but am not thrilled with it.  I think Roboform is doing the same thing with the free version, meaning it doesn't always work properly and I get error messages.  If I purchased  Roboform Pro magically everything  would work properly.