I am really stuck up with this issue :-(
1. Initially I had connected SalesForce with my own WebService Endpoint.
I had created a mapping - which compared the last_mod_date with created_date and sends a status 'updated' / 'new' to my web service. This was working fine.
2. Then I introduced one more step just after connecting to SalesForce - to filter out 'existing' record. So I created a map to find if incoming records are newer than the Last_Run_Date of process and stores the status in an xml file. This step with custom Groovy Script also worked just fine.
But now step #1 is broken !!
The process fails to send the records to my webservice and I receive the error - 'First document failure: No data produced from map 'DCS-SFDC-Dell-Mapping-3', please check source profile and make sure it matches source data.'
An early favour is solicited !