Index: src/java/org/apache/lucene/index/StoredFieldsWriter.java
===================================================================
--- src/java/org/apache/lucene/index/StoredFieldsWriter.java	(revision 808531)
+++ src/java/org/apache/lucene/index/StoredFieldsWriter.java	(working copy)
@@ -91,8 +91,10 @@
       state.docWriter.removeOpenFile(state.docStoreSegmentName + "." + IndexFileNames.FIELDS_EXTENSION);
       state.docWriter.removeOpenFile(state.docStoreSegmentName + "." + IndexFileNames.FIELDS_INDEX_EXTENSION);
 
-      if (4+((long) state.numDocsInStore)*8 != state.directory.fileLength(state.docStoreSegmentName + "." + IndexFileNames.FIELDS_INDEX_EXTENSION))
-        throw new RuntimeException("after flush: fdx size mismatch: " + state.numDocsInStore + " docs vs " + state.directory.fileLength(state.docStoreSegmentName + "." + IndexFileNames.FIELDS_INDEX_EXTENSION) + " length in bytes of " + state.docStoreSegmentName + "." + IndexFileNames.FIELDS_INDEX_EXTENSION);
+      final String fileName = state.docStoreSegmentName + "." + IndexFileNames.FIELDS_INDEX_EXTENSION;
+
+      if (4+((long) state.numDocsInStore)*8 != state.directory.fileLength(fileName))
+        throw new RuntimeException("after flush: fdx size mismatch: " + state.numDocsInStore + " docs vs " + state.directory.fileLength(fileName) + " length in bytes of " + fileName + " file exists?=" + state.directory.fileExists(fileName));
     }
   }
 
Index: src/java/org/apache/lucene/index/SegmentMerger.java
===================================================================
--- src/java/org/apache/lucene/index/SegmentMerger.java	(revision 808531)
+++ src/java/org/apache/lucene/index/SegmentMerger.java	(working copy)
@@ -357,7 +357,8 @@
         fieldsWriter.close();
       }
 
-      final long fdxFileLength = directory.fileLength(segment + "." + IndexFileNames.FIELDS_INDEX_EXTENSION);
+      final String fileName = segment + "." + IndexFileNames.FIELDS_INDEX_EXTENSION;
+      final long fdxFileLength = directory.fileLength(fileName);
 
       if (4+((long) docCount)*8 != fdxFileLength)
         // This is most likely a bug in Sun JRE 1.6.0_04/_05;
@@ -365,7 +366,7 @@
         // throw an exception to prevent the corruption from
         // entering the index.  See LUCENE-1282 for
         // details.
-        throw new RuntimeException("mergeFields produced an invalid result: docCount is " + docCount + " but fdx file size is " + fdxFileLength + "; now aborting this merge to prevent index corruption");
+        throw new RuntimeException("mergeFields produced an invalid result: docCount is " + docCount + " but fdx file size is " + fdxFileLength + " file=" + fileName + " file exists?=" + directory.fileExists(fileName) + "; now aborting this merge to prevent index corruption");
 
     } else
       // If we are skipping the doc stores, that means there
@@ -487,7 +488,8 @@
       termVectorsWriter.close();
     }
 
-    final long tvxSize = directory.fileLength(segment + "." + IndexFileNames.VECTORS_INDEX_EXTENSION);
+    final String fileName = segment + "." + IndexFileNames.VECTORS_INDEX_EXTENSION;
+    final long tvxSize = directory.fileLength(fileName);
 
     if (4+((long) mergedDocs)*16 != tvxSize)
       // This is most likely a bug in Sun JRE 1.6.0_04/_05;
@@ -495,7 +497,7 @@
       // throw an exception to prevent the corruption from
       // entering the index.  See LUCENE-1282 for
       // details.
-      throw new RuntimeException("mergeVectors produced an invalid result: mergedDocs is " + mergedDocs + " but tvx size is " + tvxSize + "; now aborting this merge to prevent index corruption");
+      throw new RuntimeException("mergeVectors produced an invalid result: mergedDocs is " + mergedDocs + " but tvx size is " + tvxSize + " file=" + fileName + " file exists?=" + directory.fileExists(fileName) + "; now aborting this merge to prevent index corruption");
   }
 
   private void copyVectorsWithDeletions(final TermVectorsWriter termVectorsWriter,
Index: src/java/org/apache/lucene/index/TermVectorsTermsWriter.java
===================================================================
--- src/java/org/apache/lucene/index/TermVectorsTermsWriter.java	(revision 808531)
+++ src/java/org/apache/lucene/index/TermVectorsTermsWriter.java	(working copy)
@@ -90,8 +90,9 @@
       tvd.close();
       tvx = null;
       assert state.docStoreSegmentName != null;
-      if (4+((long) state.numDocsInStore)*16 != state.directory.fileLength(state.docStoreSegmentName + "." + IndexFileNames.VECTORS_INDEX_EXTENSION))
-        throw new RuntimeException("after flush: tvx size mismatch: " + state.numDocsInStore + " docs vs " + state.directory.fileLength(state.docStoreSegmentName + "." + IndexFileNames.VECTORS_INDEX_EXTENSION) + " length in bytes of " + state.docStoreSegmentName + "." + IndexFileNames.VECTORS_INDEX_EXTENSION);
+      final String fileName = state.docStoreSegmentName + "." + IndexFileNames.VECTORS_INDEX_EXTENSION;
+      if (4+((long) state.numDocsInStore)*16 != state.directory.fileLength(fileName))
+        throw new RuntimeException("after flush: tvx size mismatch: " + state.numDocsInStore + " docs vs " + state.directory.fileLength(fileName) + " length in bytes of " + fileName + " file exists?=" + state.directory.fileExists(fileName));
 
       state.flushedFiles.add(state.docStoreSegmentName + "." + IndexFileNames.VECTORS_INDEX_EXTENSION);
       state.flushedFiles.add(state.docStoreSegmentName + "." + IndexFileNames.VECTORS_FIELDS_EXTENSION);