When I have an editor open with a pinned grid and an editor opened with an un-pinned grid, if I run a query in the editor with the pinned grid and then toggle over to the editor with the un-pinned grid, the un-pinned grid becomes un-hidden and is hard to get hidden again. You have to click around on the editor a couple of times before it goes back down.
Waiting for fix to be released in a future version of Toad for Oracle.
This is fixed in the beta version (11.6) of Toad. The beta version can be downloaded from...