We had a number of clients this week whose Outlook started having all kinds of issues including regularly crashing, opening in safe mode by default, and losing certain preferences (reading pane closed and text format in new email had defaulted). This seemed to happen in particular with Windows 7 Pro and Office 2010 Home & Business.
After trying all kinds fixes we found that the issue was caused by Outlook updates that had recently been installed. So we uninstalled updates KB2760779, KB3101535 and KB2553308 and restarted the computer. Result: Outlook seems to be as good as new. No more crashing, no more safe mode and all preferences returned.
Clearly there is a bug in one of the updates, so hopefully Microsoft will resolve this shortly, but in the meantime roll back these 3 updates and make sure you set them to 'hidden' to avoid the updates installing again automatically.