diff --git a/widget/src/mac/nsClipboard.cpp b/widget/src/mac/nsClipboard.cpp
index 0458fab963b..55e0f4cdb4b 100644
--- a/widget/src/mac/nsClipboard.cpp
+++ b/widget/src/mac/nsClipboard.cpp
@@ -68,11 +68,16 @@
 #include "nsStylClipboardUtils.h"
 #include "nsLinebreakConverter.h"
 #include "nsAutoPtr.h"
+#include "nsIServiceManager.h"
+#include "nsIMacUtils.h"
 
 #include <Scrap.h>
 #include <Script.h>
 #include <TextEdit.h>
 
+static const PRUint32 kPrivateFlavorMask = 0xffff0000;
+static const PRUint32 kPrivateFlavorTag = 'MZ..' & kPrivateFlavorMask;
+
 
 
 //
@@ -330,10 +335,30 @@ nsresult
 nsClipboard :: PutOnClipboard ( ResType inFlavor, const void* inData, PRInt32 inLen )
 {
   nsresult errCode = NS_OK;
+
+  void* data = (void*) inData;
+  if ((inFlavor & kPrivateFlavorMask) == kPrivateFlavorTag) {
+    // Byte-swap private flavors if running translated
+    nsCOMPtr<nsIMacUtils> macUtils =
+     do_GetService("@mozilla.org/xpcom/mac-utils;1");
+    PRBool isTranslated;
+    if (macUtils &&
+        NS_SUCCEEDED(macUtils->GetIsTranslated(&isTranslated)) &&
+        isTranslated) {
+      data = nsMemory::Alloc(inLen);
+      if (!data)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+      swab(inData, data, inLen);
+    }
+  }
   
   ScrapRef scrap;
   ::GetCurrentScrap(&scrap);
-  ::PutScrapFlavor( scrap, inFlavor, kScrapFlavorMaskNone, inLen, inData );
+  ::PutScrapFlavor( scrap, inFlavor, kScrapFlavorMaskNone, inLen, data );
+
+  if (data != inData)
+    nsMemory::Free(data);
 
   return errCode;
   
@@ -557,6 +582,26 @@ nsClipboard :: GetDataOffClipboard ( ResType inMacFlavor, void** outData, PRInt3
       return NS_ERROR_FAILURE;
     }
 
+    if ((inMacFlavor & kPrivateFlavorMask) == kPrivateFlavorTag) {
+      // Byte-swap private flavors if running translated
+      nsCOMPtr<nsIMacUtils> macUtils =
+       do_GetService("@mozilla.org/xpcom/mac-utils;1");
+      PRBool isTranslated;
+      if (macUtils &&
+          NS_SUCCEEDED(macUtils->GetIsTranslated(&isTranslated)) &&
+          isTranslated) {
+        char* swappedData = (char*) nsMemory::Alloc(dataSize);
+        if (!swappedData) {
+          nsMemory::Free(dataBuff);
+          return NS_ERROR_OUT_OF_MEMORY;
+        }
+
+        swab(dataBuff, swappedData, dataSize);
+        nsMemory::Free(dataBuff);
+        dataBuff = swappedData;
+      }
+    }
+
     // put it into the transferable
     if ( outDataSize )
       *outDataSize = dataSize;
diff --git a/widget/src/mac/nsDragService.cpp b/widget/src/mac/nsDragService.cpp
index b7bcd12acc0..ebbd5dea56a 100644
--- a/widget/src/mac/nsDragService.cpp
+++ b/widget/src/mac/nsDragService.cpp
@@ -60,6 +60,7 @@
 #include "nsCRT.h"
 #include "nsPrimitiveHelpers.h"
 #include "nsLinebreakConverter.h"
+#include "nsIMacUtils.h"
 
 #include "nsIContent.h"
 #include "nsIDOMNode.h"
@@ -104,6 +105,9 @@ GetPrimaryFrameFor(nsIContent* aContent)
   return result;
 }
 
+static const PRUint32 kPrivateFlavorMask = 0xffff0000;
+static const PRUint32 kPrivateFlavorTag = 'MZ..' & kPrivateFlavorMask;
+
 
 static void
 SetPortToKnownGoodPort()
@@ -793,6 +797,26 @@ nsDragService::DragSendDataProc(FlavorType inFlavor, void* inRefCon, ItemReferen
     PRUint32 dataSize = 0;
     retVal = dragService->GetDataForFlavor(dragService->mDataItems, inDragRef, inItemRef, inFlavor, &data, &dataSize);
     if ( retVal == noErr ) {      
+        if ((inFlavor & kPrivateFlavorMask) == kPrivateFlavorTag) {
+          // Byte-swap private flavors if running translated
+          nsCOMPtr<nsIMacUtils> macUtils =
+           do_GetService("@mozilla.org/xpcom/mac-utils;1");
+          PRBool isTranslated;
+          if (macUtils &&
+              NS_SUCCEEDED(macUtils->GetIsTranslated(&isTranslated)) &&
+              isTranslated) {
+            char* swappedData = (char*) nsMemory::Alloc(dataSize);
+            if (!swappedData) {
+              nsMemory::Free(data);
+              return notEnoughMemoryErr;
+            }
+            else {
+              swab(data, swappedData, dataSize);
+              nsMemory::Free(data);
+              data = swappedData;
+            }
+          }
+        }
         // make the data accessible to the DragManager
         retVal = ::SetDragItemFlavorData ( inDragRef, inItemRef, inFlavor, data, dataSize, 0 );
         NS_ASSERTION ( retVal == noErr, "SDIFD failed in DragSendDataProc" );
@@ -1095,7 +1119,27 @@ nsDragService::ExtractDataFromOS ( DragReference inDragRef, ItemReference inItem
     buff = NS_REINTERPRET_CAST(char*, nsMemory::Alloc(buffSize + 1));
     if ( buff ) {	     
       err = ::GetFlavorData ( inDragRef, inItemRef, inFlavor, buff, &buffSize, 0 );
-      if ( err ) {
+      if (err == noErr) {
+        if ((inFlavor & kPrivateFlavorMask) == kPrivateFlavorTag) {
+          // Byte-swap private flavors if running translated
+          nsCOMPtr<nsIMacUtils> macUtils =
+           do_GetService("@mozilla.org/xpcom/mac-utils;1");
+          PRBool isTranslated;
+          if (macUtils &&
+              NS_SUCCEEDED(macUtils->GetIsTranslated(&isTranslated)) &&
+              isTranslated) {
+            char* swappedData = (char*) nsMemory::Alloc(buffSize);
+            if (!swappedData)
+              retval = NS_ERROR_OUT_OF_MEMORY;
+            else {
+              swab(buff, swappedData, buffSize);
+              nsMemory::Free(buff);
+              buff = swappedData;
+            }
+          }
+        }
+      }
+      else {
         #ifdef NS_DEBUG
           printf("nsDragService: Error getting data out of drag manager, #%d\n", err);
         #endif
diff --git a/xpcom/base/nsIMacUtils.idl b/xpcom/base/nsIMacUtils.idl
index e0ae0991e4b..5c5fe56699d 100644
--- a/xpcom/base/nsIMacUtils.idl
+++ b/xpcom/base/nsIMacUtils.idl
@@ -41,7 +41,7 @@
  * nsIMacUtils: Generic globally-available Mac-specific utilities.
  */
 
-[scriptable, uuid(59BE3453-873B-450D-8DB8-2643E08A00BE)]
+[scriptable, uuid(F6FC107C-5CBA-4C5C-A35E-B69D580D1DB6)]
 interface nsIMacUtils : nsISupports
 {
   /**
@@ -49,4 +49,9 @@ interface nsIMacUtils : nsISupports
    * ppc and x86 (universal binary).
    */
   readonly attribute boolean isUniversalBinary;
+
+  /**
+   * True when running under binary translation (Rosetta).
+   */
+  readonly attribute boolean isTranslated;
 };
diff --git a/xpcom/base/nsMacUtilsImpl.cpp b/xpcom/base/nsMacUtilsImpl.cpp
index 0a6c0f00aee..8eead37b9c6 100644
--- a/xpcom/base/nsMacUtilsImpl.cpp
+++ b/xpcom/base/nsMacUtilsImpl.cpp
@@ -40,6 +40,7 @@
 #include <CoreFoundation/CoreFoundation.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <sys/sysctl.h>
 #include <mach-o/fat.h>
 
 NS_IMPL_ISUPPORTS1(nsMacUtilsImpl, nsIMacUtils)
@@ -123,3 +124,31 @@ done:
 
   return NS_OK;
 }
+
+/* readonly attribute boolean isTranslated; */
+// True when running under binary translation (Rosetta).
+NS_IMETHODIMP nsMacUtilsImpl::GetIsTranslated(PRBool *aIsTranslated)
+{
+#ifdef __ppc__
+  static PRBool  sInitialized = PR_FALSE;
+
+  // Initialize sIsNative to 1.  If the sysctl fails because it doesn't
+  // exist, then translation is not possible, so the process must not be
+  // running translated.
+  static PRInt32 sIsNative = 1;
+
+  if (!sInitialized) {
+    size_t sz = sizeof(sIsNative);
+    sysctlbyname("sysctl.proc_native", &sIsNative, &sz, NULL, 0);
+    sInitialized = PR_TRUE;
+  }
+
+  *aIsTranslated = !sIsNative;
+#else
+  // Translation only exists for ppc code.  Other architectures aren't
+  // translated.
+  *aIsTranslated = PR_FALSE;
+#endif
+
+  return NS_OK;
+}