When I create tasks in the Task view, they don't appear and don't even show up with a spotlight search.  However when I view Outlook via Web, the new tasks are there on the server; likewise when viewing through Outlook 2010 on Windows.  

Similarly, if I check a task as completed, it does not get hidden from the local view in Outlook 2011 (as per my settings).  But it does register as completed on the Web view of the Server contents, or in Outlook on Windows.

I examined the folder properties and emptied the cache for Tasks on Mac Outlook 2011.  This wiped out the content of the Tasks view, but a new version was not downloaded from the server, unlike what was indicated in the properties view.