When working in the Query Builder, if the Object Palette is undocked, and the Owner drop down is clicked, it will give an access violation. 11.5.1.
"Access violation at address 0288FD89 in module 'Toad.exe'. Write of address 0000039C."
Dock the floating object palette window to the side of the main Toad window. To do this, click on the blue title bar of the object palette, and drag that window to the side edge of the Toad window. A gray outline will appear, and at this point, release the window. The Object Palette should now be docked and attached to the side of the main Toad window. The owner drop down tab should now be usable without error.
Issue fixed in Toad for Oracle 11.6 version available at: https://support.quest.com/SearchDownloads.aspx?dsNav=N:268435520
Issue found in 11.0 and 11.5.1