The error message below is display when querying a linked AS400 server.
Msg 7399, Level 16, State 1, Line 1 The OLE DB provider "IBMDASQL" for linked server "SQLSERVERNAME" reported an error. The provider did not give any information about the error. Msg 7330, Level 16, State 2, Line 1 Cannot fetch a row from OLE DB provider "IBMDASQL" for linked server "AS400".
Odd thing is the error is only displayed when the query is executed on the server itself and not when executed remotely on a workstation.
In the Provider Options (under Linked Servers in SQL Server Management Studio), for IBMDASQL, ensure that "Allow inprocess" is selected.