Hi Arthur.
We have a custom report which when executed displays a standard ALV output.
When we execute it 
It runs without any dump.
Now if we deselect the Requisition of Po from column set as shown below.
Now we encounter a dump.
Also if we try to add other columns to the column set keeping Requisition of PO in the column set it doesnot give dump but in case we add any column but exclude Requisition of PO it gives up dump.
Regards,
Rahul
We are executing this for Downloading spreadsheet as local file.