There's a big white box at the bottom of the macro browser. It seems to only happen after the first time you choose a suggested macro from the dropdown box.

See Anna Dominquez's blitz test page for screenshot:
https://extranet.atlassian.com/display/QA/2010-05-31+-+Confluence+-+3.3-beta1+-+Blitz+Test+Part+1+-+Editor+-+Anna+Dominguez's+Findings