I have boot camp installed on my MacBook Pro with Excel for both Windows and Mac. I have Excel files that is "shared" but when I try to open them in Lion after working on them Windows 7, they open as "(read only) (shared)"! It seems that they open just fine in Windows after working on them in Lion and saving there. I restart the MacBook in order to make sure that there isn't another "owner" of an open file. Anyone has an idea what to do, it is extremely frustrating.