Microsoft released a new patch today that can have some unexpected consequences on installation. After applying this mandatory patch your Outlook may experience a long delay the first time that it opens as it updates your email archive files.
Microsoft really needs to do a better job in letting their users know about things like this ahead of time. Depending on how many archives you have and how big they are opening Outlook after this patch can take upwards of half an hour... very inconvenient if you were just expecting a quick reboot, ans surely a pain if you expected to start up a patched computer in the morning and get to work.
If you haven't applied the update yet, I recommend setting aside some time to do it and then opening Outlook and letting it run overnight to avoid staring at a "Preparing Outlook for first use" message for half an hour.