We're suffering from the same error now, albeit on sqlsrv2008 and on 64bit:
Msg 7340, Level 16, State 4, Procedure prcGETDATA, Line 39
Cannot create a column accessor for OLE DB provider "IBMDASQL" for linked server "i5v5r4".
Clicking on the properties of the linked server does indeed fix the problem for a while, which is mysterious, to say the least.
Dropping and recreating the linked server does not get any results, the error perists, so I assume it has got to be something in the way the OLEDB IBMDASQL driver is being initialized or used.
Another way to (temporarily) get rid of the error is to schedule an SSIS package, which transfers a few bits of dummy data in a data flow involving both the iSeries as well as the local SQL Server as data sources, but not using the linked server. This somehow initializes the IBMDASQL driver and gets the linked server working again.
I'm really looking for a way to permanently fix this without having to click on the properties or running dummy packages...