I just did a clean install of the new RC version and ran into a problem. Thunderbird could not download my GMail emails. It had no problem with downloading Yahoo emails. It could even send emails via GMail but could not receive them. Thunderbird would try to connect to the server and would time out. So completely uninstalled the program (no Avast on the system) and the problem remained. After restoring my system from a previous backup, all is well. It appears that something was modified during the installation.