Since updating to Avast 2015 my Windows 8.1 pic freezes while online.
Control Panel>Uninstall a Program>double click “avast”>click “repair”>reboot
Some more info about your system and what other programs are running alongside avast would be helpful.
If after running a repair doesn’t work then I’d suggest a clean install using the avastclear tool.
If your issue relates to having K9 installed with Avast then as the Avast team member mentioned in the other topic you posted in https://forum.avast.com/index.php?topic=159243.msg1159584 it will be fixed when the next SP is released.