Please provide the information that makes you think avast! is blocking these?
I strongly doubt that avast! is blocking anything, it is not designed to do that, only scan files that are accessed. It is what an on-access (resident) scanner does, this is not blocking. When I run AdAware or Spybot S&D I pause the Standard Shield provider so it doesn't scan the files that are being checked by my anti-spyware/adware programs.
Check your firewall settings and ensure that your Spyware DR auto update is allowed access to the internet.