I have had no issues with Avast and have been using it for a bit now. I haven't tried AVG, but I hear it does well too. There isn't an anti virus software out that will trap all of the virus's 100% of the time. In order to ensure that your system stays clean there are a couple of things I would recommend and even that isn't a sure thing.
First off, if you are not already using one, get a router and connect to the internet through that. This will make your system less visible to threats. Second, do a full scan with anti virus as well as with malwarebyte's software to ensure that if something made it through, you find it quickly and can get rid of it. Third get the program "hijackthis" and install it. It will look for threats that are not virus's but programs that hijack your browser and will stop them.
Lastly, avoid going to sites that are potential threat areas. torrents, porn, hacked software all have a greater potential of having a virus than regular sites. If you must go to those sites, I would suggest that you run your browser in sandbox mode which is an option for Avast to use. This will prevent anything from being saved once the browser session is closed reducing the chance of getting a virus.
Now as to your issues with your system, there is a strong possibility that you did not have a virus. Corrupt drivers tend to be identified as being infected with a virus even though there is no virus in the system at all. Corruption can happen at any time with no reasoning for it. A lot of the virus's out there are not setup to mess with your system. They are designed to get information from you that the author can use at a later time. A smart virus author will write his virus so that it will be almost invisible to ensure a longer life on your system increasing the odds of getting useful information.