Keep getting this message. At the same time, three groups emptied of all contacts.
One option to consider is setting up your Outlook.com account as Exchange rather than IMAP. That usually works better as it will not use AirSync to sync the calendar and contact data.
To do that, go to Menu > Tools > Accounts and remove your Outlook.com account. Then add a new account, but instead of using the Automatic Setup, choose Mail > Exchange.