If you are on a page such as:

/admin/settings.php?section=gradessettings

Then you get a crumbtrail such as:

1. Dashboard
   /my/
2. Site administration
   /admin/search.php
3. Grades
   /admin/category.php?category=grades
4. General settings
   /admin/settings.php?section=gradessettings

But this doesn't reflect the same hierarchy link you would use to navigate there, so when you go 'back' using the crumb nodes you end up somewhere odd and not where you expect (IMHO)

Instead that would look like this:

1. Dashboard
   /my/
2. Site administration
   /admin/search.php
3. Grades
   /admin/search.php#linkgrades
4. General settings
   /admin/settings.php?section=gradessettings

Or alternatively there would actually be a 5th node inserted between the 3rd and 4th node for the category=grades node, but instead of going to that standalone node page it would deep link into the Grades tab, and then down to an link anchor for the 'Grades' or 'Report settings' sections with that tab.

Stated another way:

1) All top level node links should return a tab anchor link

2) All second level node links should return a anchor within that tab