obj.ExportEx File.qvd, 4 API Limitations to exporting a table to qvd ?

[#1]

Running in developer version 8.50.6326... I am unable to export a large pivot table to qvd through the API using the following vbscript:

SUB ExportChart
Dim Filename
Filename = \\localserverUNC\Folder\Qlikview_Table.qvd
set Graph = ActiveDocument.GetSheetObject("MyChart")
Graph.ExportEx Filename , 4
END SUB

I get the following error:

Two strange things about this:

1) This process works if the pivot table is small enough (resultant qvd size < 25 MB).
2) I can export to qvd manually (almost any size table, up to 6+ million rows and 72 columns) using the right-click, export, save as qvd.

Is there so limitations to the API or to this exportEx command? Or is there some setting somewhere that I can modify to permit large file exports to qvds?

[#2]

Martin from QlikView support recommended I point to the local drive.

When I changed the vbscript to point to a local drive letter e:\ rather than the UNC path of the SAN which we are using, the export worked!

I don't know why the UNC file path is not working. This is still an issue, as we have multiple development and production servers, with SAN attached directly to only one of these servers. So, I may want to run this process (and save the exported QVD to the SAN) on a different server than the server which has the SAN attached, thus requiring UNC.

Any thoughts on working around or through this? or Fixing this???