Thankyou very much for your answers.. I have now managed to get avast working!
It happens that I thought that I had Uninstalled Panda, but avast was stopping the uninstalling when found a virus in one of Panda's dll's.
I stopped avast and unistalled Panda again, this time without problems. After rebooting, avast and all providers are working fine, without blocking any browser. Many thanks again to all that answered my query..
Kim