What the version of the ApacheDS?
If it's 2.0.0-M13 or 2.0.0-M14, note that Apache Directory Studio 2.0.0-M7 (2.0.0.v20130517) is NOT compatible with them, since they include a new attribute type for the configuration.
Version 2.0.0-M8 has been voted to fix this issue (and more) and is currently being replicated to the Apache mirrors before being announce tomorrow.
In the meantime, you can download it here:
Could you try and tell us if it fixes your issue (it probably will)?