Index: trunk/ppMerge/src/ppMergeLoop.c
===================================================================
--- trunk/ppMerge/src/ppMergeLoop.c	(revision 24782)
+++ trunk/ppMerge/src/ppMergeLoop.c	(revision 24797)
@@ -204,4 +204,10 @@
 	    }
 
+	    int rows = psMetadataLookupS32(NULL, config->arguments, "ROWS"); // Number of rows to read per chunk
+	    if (!rows && nThreads) {
+	      psError(PS_ERR_UNKNOWN, false, "Invalid combination of threads > 0 and ROWS == 0 (ie, multiple threads working on the full array...)");
+	      goto ERROR;
+	    }
+
             ppMergeFileGroup *fileGroup = NULL;
             psArray *fileGroups = psArrayAlloc(nThreads + 1);
@@ -213,5 +219,7 @@
                     pmFPAfile *input = pmFPAfileSelectSingle(config->files, "PPMERGE.INPUT", j);
                     pmCell *inCell = pmFPAviewThisCell(view, input->fpa); ///< Input cell
-                    readouts->data[j] = pmReadoutAlloc(inCell);
+		    pmReadout *readout = pmReadoutAlloc(inCell);
+		    readout->process = true; // until proven otherwise, attempt to process this readout
+                    readouts->data[j] = readout;
                 }