The only thing I can think of is that either:
1. You changed the menu items, which also changes the link.
2. You changed sections or categories, which can effect the link.
3. You're using SEF and used the SEF version of the link instead of the actual url (ie - yoursite.com/gallery instead of the yoursite.com/component/option,com_gallery/Itemid,22...).
There might be other reasons, but these are only guesses.