diff --git a/layout/base/nsCaret.cpp b/layout/base/nsCaret.cpp
index 65ddb9f297a2..e9851f277053 100644
--- a/layout/base/nsCaret.cpp
+++ b/layout/base/nsCaret.cpp
@@ -166,9 +166,8 @@ NS_IMETHODIMP nsCaret::Init(nsIPresShell *inPresShell)
 #ifdef IBMBIDI
   PRBool isRTL = PR_FALSE;
   mBidiKeyboard = do_GetService("@mozilla.org/widget/bidikeyboard;1");
-  if (mBidiKeyboard)
-	mBidiKeyboard->IsLangRTL(&isRTL);
-  mKeyboardRTL = isRTL;
+  if (mBidiKeyboard && NS_SUCCEEDED(mBidiKeyboard->IsLangRTL(&isRTL)))
+    mKeyboardRTL = isRTL;
 #endif
   
   return NS_OK;
@@ -1084,8 +1083,11 @@ nsresult nsCaret::UpdateHookRect(nsPresContext* aPresContext)
   // Simon -- make a hook to draw to the left or right of the caret to show keyboard language direction
   PRBool bidiEnabled;
   PRBool isCaretRTL=PR_FALSE;
-  if (mBidiKeyboard)
-    mBidiKeyboard->IsLangRTL(&isCaretRTL);
+  if (!mBidiKeyboard || NS_FAILED(mBidiKeyboard->IsLangRTL(&isCaretRTL)))
+    // if mBidiKeyboard->IsLangRTL() failed, there is no way to tell the
+    // keyboard direction, or the user has no right-to-left keyboard
+    // installed, so we  never draw the hook.
+    return NS_OK;
   if (isCaretRTL)
   {
     bidiEnabled = PR_TRUE;
diff --git a/widget/public/nsIBidiKeyboard.idl b/widget/public/nsIBidiKeyboard.idl
index a462d6d62ea5..0a6b45a62845 100644
--- a/widget/public/nsIBidiKeyboard.idl
+++ b/widget/public/nsIBidiKeyboard.idl
@@ -39,17 +39,19 @@
 
 #include "nsISupports.idl"
 
-[scriptable, uuid(BB961AE1-7432-11d4-B77A-00104B4119F8)]
+[scriptable, uuid(0D8F8F10-C92D-4A6A-B2BB-E1921F3F4DDA)]
 interface nsIBidiKeyboard : nsISupports
 {
   /**
    * Determines if the current keyboard language is right-to-left
+   * @throws NS_ERROR_FAILURE if no right-to-left keyboards are installed
    */
-  void isLangRTL(out PRBool aIsRTL);
+  boolean isLangRTL();
 
   /**
    * Sets the keyboard language to left-to-right or right-to-left
    * @param aLevel - if odd set the keyboard to RTL, if even set LTR 
+   * @throws NS_ERROR_FAILURE if no right-to-left keyboards are installed
    */
   void setLangFromBidiLevel(in PRUint8 aLevel);
 };
diff --git a/widget/public/nsWidgetsCID.h b/widget/public/nsWidgetsCID.h
index 7268a082bf72..8da81b484c49 100644
--- a/widget/public/nsWidgetsCID.h
+++ b/widget/public/nsWidgetsCID.h
@@ -137,9 +137,9 @@
 #define NS_SOUND_CID \
 { 0xb148eed2, 0x236d, 0x11d3, { 0xb3, 0x5c, 0x0, 0xa0, 0xcc, 0x3c, 0x1c, 0xde } }
 
-// {2572E6B0-7439-11d4-B77A-00104B4119F8}
+// {9f1800ab-f428-4207-b40c-e832e77b01fc}
 #define NS_BIDIKEYBOARD_CID \
-{ 0x2572e6b0, 0x7439, 0x11d4, { 0xb7, 0x7a, 0x0, 0x10, 0x4b, 0x41, 0x19, 0xf8 } }
+{ 0x9f1800ab, 0xf428, 0x4207, { 0xb4, 0x0c, 0xe8, 0x32, 0xe7, 0x7b, 0x01, 0xfc } }
 
 #define NS_SCREENMANAGER_CID \
 { 0xc401eb80, 0xf9ea, 0x11d3, { 0xbb, 0x6f, 0xe7, 0x32, 0xb7, 0x3e, 0xbe, 0x7c } }
diff --git a/widget/src/beos/nsBidiKeyboard.cpp b/widget/src/beos/nsBidiKeyboard.cpp
index 8a3e478dcd14..c1e4b61b7b43 100644
--- a/widget/src/beos/nsBidiKeyboard.cpp
+++ b/widget/src/beos/nsBidiKeyboard.cpp
@@ -53,11 +53,11 @@ NS_IMETHODIMP nsBidiKeyboard::IsLangRTL(PRBool *aIsRTL)
 {
   *aIsRTL = PR_FALSE;
   // XXX Insert platform specific code to determine keyboard direction
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP nsBidiKeyboard::SetLangFromBidiLevel(PRUint8 aLevel)
 {
   // XXX Insert platform specific code to set keyboard language
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
diff --git a/widget/src/gtk/nsBidiKeyboard.cpp b/widget/src/gtk/nsBidiKeyboard.cpp
index 8a3e478dcd14..c1e4b61b7b43 100644
--- a/widget/src/gtk/nsBidiKeyboard.cpp
+++ b/widget/src/gtk/nsBidiKeyboard.cpp
@@ -53,11 +53,11 @@ NS_IMETHODIMP nsBidiKeyboard::IsLangRTL(PRBool *aIsRTL)
 {
   *aIsRTL = PR_FALSE;
   // XXX Insert platform specific code to determine keyboard direction
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP nsBidiKeyboard::SetLangFromBidiLevel(PRUint8 aLevel)
 {
   // XXX Insert platform specific code to set keyboard language
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
diff --git a/widget/src/gtk2/nsBidiKeyboard.cpp b/widget/src/gtk2/nsBidiKeyboard.cpp
index 58bdcc1260cf..ce2762175e83 100644
--- a/widget/src/gtk2/nsBidiKeyboard.cpp
+++ b/widget/src/gtk2/nsBidiKeyboard.cpp
@@ -52,11 +52,11 @@ NS_IMETHODIMP nsBidiKeyboard::IsLangRTL(PRBool *aIsRTL)
 {
     *aIsRTL = PR_FALSE;
     // XXX Insert platform specific code to determine keyboard direction
-    return NS_OK;
+    return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP nsBidiKeyboard::SetLangFromBidiLevel(PRUint8 aLevel)
 {
     // XXX Insert platform specific code to set keyboard language
-    return NS_OK;
+    return NS_ERROR_NOT_IMPLEMENTED;
 }
diff --git a/widget/src/os2/nsBidiKeyboard.cpp b/widget/src/os2/nsBidiKeyboard.cpp
index 8a3e478dcd14..c1e4b61b7b43 100644
--- a/widget/src/os2/nsBidiKeyboard.cpp
+++ b/widget/src/os2/nsBidiKeyboard.cpp
@@ -53,11 +53,11 @@ NS_IMETHODIMP nsBidiKeyboard::IsLangRTL(PRBool *aIsRTL)
 {
   *aIsRTL = PR_FALSE;
   // XXX Insert platform specific code to determine keyboard direction
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP nsBidiKeyboard::SetLangFromBidiLevel(PRUint8 aLevel)
 {
   // XXX Insert platform specific code to set keyboard language
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
diff --git a/widget/src/photon/nsBidiKeyboard.cpp b/widget/src/photon/nsBidiKeyboard.cpp
index d206dc97ffb4..ecc3e20d997b 100644
--- a/widget/src/photon/nsBidiKeyboard.cpp
+++ b/widget/src/photon/nsBidiKeyboard.cpp
@@ -53,7 +53,7 @@ NS_IMETHODIMP nsBidiKeyboard::IsLangRTL(PRBool *aIsRTL)
 #ifdef IBMBIDI
   // XXX Insert platform specific code to determine keyboard direction
 #endif
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP nsBidiKeyboard::SetLangFromBidiLevel(PRUint8 aLevel)
@@ -61,5 +61,5 @@ NS_IMETHODIMP nsBidiKeyboard::SetLangFromBidiLevel(PRUint8 aLevel)
 #ifdef IBMBIDI
   // XXX Insert platform specific code to set keyboard language
 #endif
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
diff --git a/widget/src/qt/nsBidiKeyboard.cpp b/widget/src/qt/nsBidiKeyboard.cpp
index 44464632ee90..98c5c6b69808 100644
--- a/widget/src/qt/nsBidiKeyboard.cpp
+++ b/widget/src/qt/nsBidiKeyboard.cpp
@@ -53,11 +53,11 @@ NS_IMETHODIMP nsBidiKeyboard::IsLangRTL(PRBool *aIsRTL)
 {
   *aIsRTL = PR_FALSE;
   // XXX Insert platform specific code to determine keyboard direction
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP nsBidiKeyboard::SetLangFromBidiLevel(PRUint8 aLevel)
 {
   // XXX Insert platform specific code to set keyboard language
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
diff --git a/widget/src/xlib/nsBidiKeyboard.cpp b/widget/src/xlib/nsBidiKeyboard.cpp
index 8a3e478dcd14..c1e4b61b7b43 100644
--- a/widget/src/xlib/nsBidiKeyboard.cpp
+++ b/widget/src/xlib/nsBidiKeyboard.cpp
@@ -53,11 +53,11 @@ NS_IMETHODIMP nsBidiKeyboard::IsLangRTL(PRBool *aIsRTL)
 {
   *aIsRTL = PR_FALSE;
   // XXX Insert platform specific code to determine keyboard direction
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP nsBidiKeyboard::SetLangFromBidiLevel(PRUint8 aLevel)
 {
   // XXX Insert platform specific code to set keyboard language
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }