cannot click onto new/delete/junk/etc blocks at the top of screen. Once I am in a folder cannot go back to inbox

Cannot use sign out box. Once I am reading a file in the inbox folder I cannot go back to the list of folders in the inbox.  Cannot click onto new/delete/junk/etc blocks at the top of the screen.  Am able to use those keys at the bottom of the screen.  My hotmail is working fine on my Mac computer but not on my PC.  I used Windows Vista.