The "Wiki Explorer" button still highlighted when I edit Page

When I open MS Word 2007 and I try to edit a page which is selected in the Explorer, the page opens but the Explorer disappears. I try to open the Explorer with the button but it still highlighted, so I can't reopen the Explorer.
I just notice that this problem occurs when I try to use XWord with a blank document of MS Word, but when I open a word document that was previously save , it function