I use an older version (6.5) of Aqua Data Studio (an excellent tool), but it recently broke on the Mac when Java 1.6 came out. There is a quick fix for this, as the problem was a few classes moving outside of the JRE’s default libs.
Download this file and put it in AquaDataStudio.app/Content/Resources/Java.
Someone else came up with this solution, but I have no idea of the original source.