Checkboxes not having focus when using the tab key

IN Studio, some checkboxes can't be reached with the "tab" key (and checked/unchecked from keyboard), which is a problem for the 508 compliance (for people with disabilities).

• Lists of elements: In all lists (list of document types, list of workflows, list of chains, ...): Can't select the checkboxes
• Schemas (in "Schemas, in the "Schema" tab of a document, and in the "Variables" part of workflows): Can't select the box to delete the field
• Document -> Tabs -> Default Tabs Filtering: unable to give the focus to the checkboxes
• All boxes in the "Availability" dialogs

Well, mainly, all the checkboxes