Outlook2010 won't start up loading Addin

Hi there!
My Outlook 2010 won’t start up, it keeps freezing while saying:

Loading Add-ins (3 of 14)
avast! addin

I’m on Win7 Pro 64bits Service Pack 1 with Outlook2010 and Avast Internet Security.
I use Outlook with an exchange server via https-connection.
Does anyone know what to do?
Laura