Results of Viewshed on Mosaic dataset empty?

[MichellePearson]

I made a mosaic dataset with about 200 tiles of IFSAR DSM data.  I need to run a Viewshed Analysis on an area that has probably 150 or so of the tiles.  I pulled the mosaic dataset into ArcGIS and am running the Spatial Analyist View shed tool with 5 points selected in the input point file.  The tool runs for less than a minute and tells me the Output raster: <empty>. 
What am I missing?
Thanks,
Michelle

[MelanieHarlow]

You may be running into two issues:

1. maximum request size property


2. cell size

Please review:
Using mosaic datasets and image services in geoprocessing tools
Data formats supported by Spatial Analyst

[MichellePearson]

Hi Melanie,
I'm sorry, I didn't see that anyone had answered my question.  I now have a much smaller mosaic dataset focused on our area of interest and am still running into the same problem.  Several times the Viewshed tool worked once and then wouldn't run again when I tried to run it on the next viewpoints.  Well, it acts like its running then results in an empty dataset.  Can I edit the cell size of the mosaic dataset?