I had the same problem appear after the most recent Office update - what a pain!

My resolution was similar to zatlas1: I went in to the Registry and edited:HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\E xcel\Security\FileBlock
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\E xcel\Security\ProtectedView

I deleted alll the entries in the above two registry folders which cleared all the current settings for File Block Settings. It worked and now I can once again save and open Excel files of any kind in Excel as normal.