Token Tree is inaccessible with a screenreader.

I am attempting to modify the file storage location for content attached to a page content type. when the "show replacement patterns" link is clicked, a table appears which enables the tokens to be selected. However, it is not possible when using a screenreader (voiceover on OSX 10.7.2) to expand the lists of available tokens. For example, the left-hand column has "date". When clicked, the middle column is populated with related tokens. It is not possible to populate this middle column with a screenreader.