Problem with W8 / outlook 2013

Hi (and happy new year!).

Since i have upgrade my MS-office 2010 to MS-office 2013 i have a problem linked to Avast free (i think).

After a boot, the first time i start Outlook 2013, Outlook stop when importing new mails.

I must exit, and kill Outlook in Windows 8 tasks manager (or reboot).

When i restart Outlook 2013, i have always the avast message “new virus database…” and after all is ready.

This only when i start my computer at the morning (i think when Avast need to update virus database).

All the day, if i don’t stop my computer i don’t have problem, until the next day boot.

Someone else have (or know) this problem ?

Regard.