Why should avast “make” it work in a beta? The whole point in “beta” is to work out the kinks.
When what really matters is the final product. FF 4.0.1 is just out of the box. As far as entering a site with a virus or malware…why should I infect my pc? The whole point of an anti-virus is to avoid that garbage. That is why I trust the eight resident shields that avast provides.