diff --git a/mozilla/embedding/browser/gtk/src/EmbedStream.cpp b/mozilla/embedding/browser/gtk/src/EmbedStream.cpp
index b53e91b37bb..641c8f0e234 100644
--- a/mozilla/embedding/browser/gtk/src/EmbedStream.cpp
+++ b/mozilla/embedding/browser/gtk/src/EmbedStream.cpp
@@ -271,6 +271,9 @@ EmbedStream::ReadSegments(nsWriteSegmentFun aWriter, void * aClosure,
     // XXX writeCount may be less than nBytes!!  This is the wrong
     // way to synthesize ReadSegments.
     NS_ASSERTION(writeCount == nBytes, "data loss");
+
+    // errors returned from the writer end here!
+    rv = NS_OK;
   }
 
   nsMemory::Free(readBuf);
diff --git a/mozilla/embedding/browser/photon/src/EmbedStream.cpp b/mozilla/embedding/browser/photon/src/EmbedStream.cpp
index 9000df35ffd..b3a9e14039d 100644
--- a/mozilla/embedding/browser/photon/src/EmbedStream.cpp
+++ b/mozilla/embedding/browser/photon/src/EmbedStream.cpp
@@ -272,6 +272,9 @@ EmbedStream::ReadSegments(nsWriteSegmentFun aWriter, void * aClosure,
     // XXX writeCount may be less than nBytes!!  This is the wrong
     // way to synthesize ReadSegments.
     NS_ASSERTION(writeCount == nBytes, "data loss");
+
+    // errors returned from the writer end here!
+    rv = NS_OK;
   }
 
   nsMemory::Free(readBuf);
diff --git a/mozilla/modules/libjar/nsJARInputStream.cpp b/mozilla/modules/libjar/nsJARInputStream.cpp
index 6fa2dadcdfb..43527af2e8f 100644
--- a/mozilla/modules/libjar/nsJARInputStream.cpp
+++ b/mozilla/modules/libjar/nsJARInputStream.cpp
@@ -75,6 +75,9 @@ nsJARInputStream::ReadSegments(nsWriteSegmentFun writer, void * closure, PRUint3
      // XXX _retval may be less than nBytes!!  This is the wrong
      // way to synthesize ReadSegments.
      NS_ASSERTION(*_retval == nBytes, "data loss");
+
+     // errors returned from the writer end here! 
+     rv = NS_OK;
    }
  
    nsMemory::Free(readBuf);
diff --git a/mozilla/netwerk/base/src/nsBufferedStreams.cpp b/mozilla/netwerk/base/src/nsBufferedStreams.cpp
index c377699ccf2..8493482938c 100644
--- a/mozilla/netwerk/base/src/nsBufferedStreams.cpp
+++ b/mozilla/netwerk/base/src/nsBufferedStreams.cpp
@@ -302,7 +302,11 @@ nsBufferedInputStream::ReadSegments(nsWriteSegmentFun writer, void * closure, PR
         if (amt > 0) {
             PRUint32 read = 0;
             rv = writer(this, closure, mBuffer + mCursor, mCursor, amt, &read);
-            if (NS_FAILED(rv)) break;
+            if (NS_FAILED(rv)) {
+                // errors returned from the writer end here!
+                rv = NS_OK;
+                break;
+            }
             *result += read;
             count -= read;
             mCursor += read;
diff --git a/mozilla/rdf/base/src/nsRDFXMLDataSource.cpp b/mozilla/rdf/base/src/nsRDFXMLDataSource.cpp
index ab41aaa4cbe..671949cdfdf 100644
--- a/mozilla/rdf/base/src/nsRDFXMLDataSource.cpp
+++ b/mozilla/rdf/base/src/nsRDFXMLDataSource.cpp
@@ -184,9 +184,11 @@ public:
 
         *_retval = 0;
         nsresult rv = writer (this, closure, mBuffer+mIndex, mIndex, readCount, _retval);
-        mIndex += *_retval;
+        if (NS_SUCCEEDED(rv))
+            mIndex += *_retval;
 
-        return rv;
+        // do not propogate errors returned from writer!
+        return NS_OK;
     }
 
     NS_IMETHOD IsNonBlocking(PRBool *aNonBlocking) {
diff --git a/mozilla/xpcom/io/nsByteArrayInputStream.cpp b/mozilla/xpcom/io/nsByteArrayInputStream.cpp
index 05ac1ff165a..5779125c949 100644
--- a/mozilla/xpcom/io/nsByteArrayInputStream.cpp
+++ b/mozilla/xpcom/io/nsByteArrayInputStream.cpp
@@ -83,7 +83,6 @@ nsByteArrayInputStream::Read (char* aBuffer, PRUint32 aCount, PRUint32 *aNumRead
 NS_IMETHODIMP 
 nsByteArrayInputStream::ReadSegments(nsWriteSegmentFun writer, void * aClosure, PRUint32 aCount, PRUint32 *aNumRead)
 {
-    nsresult rv = NS_OK;
     if (aNumRead == NULL)
         return NS_ERROR_NULL_POINTER;
 
@@ -97,14 +96,16 @@ nsByteArrayInputStream::ReadSegments(nsWriteSegmentFun writer, void * aClosure,
         PRUint32 readCount = PR_MIN(aCount, (_nbytes - _pos));
         if (_buffer == NULL)
             *aNumRead = 0;
-        else 
-            rv = writer (this, aClosure, &_buffer[_pos], 
-                         _pos, readCount, aNumRead);
-        
-        _pos += *aNumRead;
+        else {
+            nsresult rv = writer (this, aClosure, &_buffer[_pos], 
+                                  _pos, readCount, aNumRead);
+            if (NS_SUCCEEDED(rv))
+                _pos += *aNumRead;
+        }
     }
 
-    return rv;
+    // do not propogate errors returned from writer!
+    return NS_OK;
 }
 
 NS_IMETHODIMP