I know this is an old thread, but I wanted to add that this issue is still happening. The only way for me to access blocked sites is to completely disable avast and kill the process with the task manager so I won't be renewing my license, but will check out this thread in the future to see if it is ever fixed.
For me it's a much larger issue because sites that I am required to access for school are blocked, as well as some shopping sites. (I can't submit homework if the university subdomain is blocked, and there's no way that blocking such sites should even happen!) Multiple people commented that we should all blindly follow the advice of the program to tell us what is and is not safe, but more often than not I am blocked from accessing sites I absolutely know to be safe. People would be livid if their ISP decided what they should and should not do on the internet, even if the ISP said it was just blocking content they know to be dangerous. In one case the FBI pulled bad websites, but made a mistake and pulled entire swath of safe family friendly websites and it was a huge issue. Ultimately, the end user - or at least the administrator account - should have the right to white list sites.
Besides that, it doesn't do a very good job of blocking sites. Avast says: "this site could have harmed your computer" , but does not actually block the site from appearing or it's code from loading in the background. If it was pushing malicious code it's unlikely that avast would do anything about that. All it does is block the user from interacting with the site which is stupid. At least when google does it they fully redirect away which prevents malicious code from running at all and then gives the user the choice to go through.
The system would be more robust if I could both white list and black list sites. I have seen numerous unsafe websites I wish could not come up via popup, but at not at all blocked. If I could specify the url with a wildcard * to indicate everything in a range should be blocked that would stop that issue and make my computer safer without depending on avast to decide it's dangerous before blocking. Likewise, if I need to access a website for work or school I should not have to completely disable an antivirus because avast has decided on it's own that it wants to control my browsing habits. I should be able to tell it to let me access a website regardless of what it is programmed to think about that.
EDIT: Killing the avast process didn't help either, so I was forced to completely uninstall. It apparently injected code into the browser which I consider to be malicious behavior. I won't be re-installing. After uninstalling, and without having to restart the computer or even restart the browser, I regained control over my computer and was able to access blocked sites again.