HELP! Trojan Horse detected every time any facebook url is opened

Every time i try to access facebook Avast! blocks the page and informs me a Trojan Horse has been detected…
Using Google Chrome and both that and Avast! are up to date.

HELP.

try running a manuall avast update…

did that help…as this should be fixed earlier today. http://forum.avast.com/index.php?topic=126381.0