SYMPTOM:
In the Duplication.log, there are many ‘ Saving’ message with null object name seen as shown in the image below:
[3/6/2014 2:16:32 PM][Derived Element] Saving '' [3/6/2014 2:16:32 PM][Derived Element] Copying:

NOTE: if the issue is not resolved after executing 'delete unused managed objects', refer to the following technical noteKB46453: Certain unused managed objects are not deleted after performing ‘delete unused managed objects’ in MicroStrategy Developer 9.x and 10.x.